A large wooden inn in the mountains
Photo information

Tohoku · Onsen area

Sukayu Onsen

すかゆ · 酸ヶ湯

Aomori · 青森市

OpenNational Health Resort Onsen100 Onsen to Know Japan — No. 9
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Official classification

Spring type (therapeutic classes)

Official spring-type name (as recorded)Acidic sulfur spring (gypsum-bearing, acidic hydrogen-sulfide type), hypotonic

Source temperature
Unconfirmed
pH
Unconfirmed
Flow rate
Unconfirmed
Radon
Unconfirmed

Appearance & feel

Water colour · Feel

Milky white

Colour and feel are listed only where a source states them. They vary by day and by bath.

What makes it special

A 160-tatami bathhouse of hiba cypress without a single pillar, where men and women share acidic water under Japan's deepest snow.
Why?

The Hiba Sennin-buro at Sukayu is a 160-tatami (about 260 m²) mixed-gender bath hall built entirely of hiba cypress with no pillars, fed by four springs. The water is an acidic sulfur spring. The Sukayu weather station recorded 566 cm of snow on 26 February 2013.[2][1]

Facilities in this area

Facilities come from the register (Wikipedia, OpenStreetMap, official sites). Those marked "natural spring unconfirmed" are listed on the basis of their name only.

Ryokan (inn) · Open

Sukayu Onsen Ryokan (Hiba Sennin-buro and Tama-no-yu)

Day-use bathing
Yes
Fee
¥1,500checked 2026-10-09
Hours
9:00–16:00(2026年12月1日から)checked 2026-10-09
Baths2
TypeGenderSourceBath temperatureFree-flowingAdded waterHeatedRecirculatedDisinfected
Mixed bathingMixedFour springs: Hot, Cool, Four-Six and waterfallUnconfirmedYes[2][6]Unconfirmed[2][6]Unconfirmed[2][6]Unconfirmed[2][6]Unconfirmed[2][6]
Indoor bathSeparateA different source from the Sennin-buroUnconfirmedUnconfirmed[2]Unconfirmed[2]Unconfirmed[2]Unconfirmed[2]Unconfirmed[2]

Getting there

Reachable by public transport

JR Bus Tohoku's Mizuumi service (Towada-kita line) takes about 1 h 10 min from Aomori Station's east exit or 1 h 20 min from Shin-Aomori to the Sukayu Onsen-mae stop. Overnight guests can book a free shuttle from Shin-Aomori (about 60 min). In winter the Towada-bound buses terminate at Sukayu.

Getting there
Aomori Station · 70
Through the year
In winter four-wheel drive or chains are required and roads are not cleared after 17:00. Buses beyond Sukayu to Lake Towada do not run from mid-November until spring
Checked
2026-10-09

About the water

As the name 'acid bath' suggests, the water is a strongly acidic sulfur spring: milky white, sulfur-scented, and it stings eyes and cuts. The Sennin-buro has tubs of different heat; the 'Four-Six' bath is said to feel four parts on the body and six on the mind, meaning it seems cooler than it is. The inn says all five of its sources are acidic sulfur springs and posts neuralgia and muscle pain among the indications. Sensitive skin should start with short soaks, and soap cannot be used.

Indications (as posted on the analysis)

Posted: neuralgia, muscle and joint pain, frozen shoulder, motor paralysis, chronic digestive complaints and others

Indications are an official statement based on the water analysis, not a guarantee of treatment. They are kept separate from opinions.

SourceSource temperaturepHRadonChecked
Hot Bath, Cool Bath, Four-Six Bath and waterfall (Sennin-buro)UnconfirmedUnconfirmedUnconfirmedno check date

Three things not to miss

A large wooden inn in the mountains
Photo information
01

Hiba Sennin-buro (Thousand-Person Bath)

In the main building A 160-tatami hall of hiba cypress with four springs: the Hot Bath, the Cool Bath, the 'Four-Six' Bath and a waterfall shower. Changing rooms are separate and a marker divides the hall by gender. Women only 8:00–9:00 daily. Bathing garments rent for 500 yen; your own are not allowed.

One of the few places left to experience Japan's mixed-bathing tradition, rules intact.[2][3]

02

Life in the toji wing

Buildings 2 to 6 Of 139 rooms, the toji wing offers plain tatami rooms where guests cook for themselves. Sukayu was one of the first three National Recuperation Hot Spring Areas designated in 1954, and this is the toji tradition in its original form.

An inn where the days spent walking to the bath are the point.[2][4]

An inn surrounded by deep snow
Photo information
03

Japan's deepest snow and the Hakkoda mountains

West flank of the Hakkoda range at about 900 m The Sukayu station recorded 566 cm of snow on 26 Feb 2013, the deepest ever at a Japanese weather station. Open year-round since 1982; in winter four-wheel drive or chains are a must and roads are not cleared after 17:00.

Steam rising between walls of snow, found nowhere else.[1][5]

The story

From Deer Bath to Acid Bath

The spring is said to have opened in 1684. A wounded deer was supposedly healed here, so it was called Shikayu, 'deer bath'; the sound slid to 'Sukayu' and the characters for 'acid bath' were fitted to the sharp water. The present company dates from 1933. In 1954 Sukayu, together with Shima and Nikko-Yumoto, became the first National Recuperation Hot Spring Areas in Japan.[1][6][4]

160 tatami without a pillar

The Sennin-buro is built solely of Aomori hiba cypress, and its 160-tatami hall has not one pillar. Two large tubs — the Hot Bath and the Four-Six Bath — plus the Cool Bath and a waterfall shower each draw on a different source. The hall is mixed, but changing rooms are separate, a marker divides the floor, and from 8 to 9 each morning it is women-only. Bathing garments must be the inn's own rental or purchase items.[2][3]

A toji inn that stays open through the snow

Sukayu sits at about 900 m on the western flank of the Hakkoda range, where some 17 m of snow falls each winter and drifts exceed 5 m. The inn used to close from November to February but has operated year-round since 1982. On 26 February 2013 the local station measured 566 cm, a national record. Roads are not ploughed after 17:00 in winter, so the rule is to arrive before dark.[1][5]

Going solo

Easy for solo travellersUnconfirmed
Weekend / peak restrictionsUnconfirmed
Where to eat dinnerThe inn's dining room and shop; nothing else nearby. Toji rooms allow self-catering
Private bathUnconfirmed

checked 2026-10-09

Through the year

Recommended months

Months open

JanFebMarAprMayJunJulAugSepOctNovDec

"Recommended" and "open" are recorded separately. Check the season for seasonal springs.

Jan · Feb · Mar — Deepest snow (record 566 cm); rime-coated 'snow monsters' and skiing on Hakkoda

Jul · Aug — Trailhead for Mt Odake; alpine flowers

Oct — Autumn colours on Hakkoda and in Oirase; extra buses toward Lake Towada

Nov — Annual closure (16–18 Nov 2026); Towada buses stop running

Food, culture & experiences

Available / bookable

Jigokunuma pond

A hot volcanic pond close to the inn[1]

About 10 min walk from the inn

Editors' guide

Just over an hour from Aomori Station on the Mizuumi bus. Buy a ticket from the machine; women can choose the 8–9 am women-only hour or rent a bathing garment (500 yen). Move between the Hot and Four-Six baths in the great hall, then finish in the gender-separated Tama-no-yu. Day use runs 9:00–16:00 (last entry 15:30), so a morning bus in and afternoon bus out fits neatly. In winter, head down before dark.

The "editors' guide" above is written by the editors from sources; it is not a visitor's opinion.

Visitor reviews

No reviews yet. While the review platform is being prepared, we do not display fictional reviews or ratings.

Review posting is in preparation, with visit date, facility, comments on water, scenery and access, photos, language and reporting.

Overview

Sukayu Onsen (酸ヶ湯, Sukayu) is an onsen (hot spring) in the Hakkōda Mountains in the city of Aomori, Aomori Prefecture in Japan. It is known for its "Sen-nin-buro" or "Bath of a thousand bathers", a large mixed gender public bath.

This overview is based on the lead section of the English Wikipedia article (CC BY-SA 4.0). View original page

Unconfirmed & notes

  • Measured pH and source temperature not on official pages (Wikipedia: 48–64°C, pH under 2)
  • Legal water-treatment notice and single-occupancy rates not confirmed
  • JR Bus fares and frequency not confirmed

Sources

  1. 酸ヶ湯 - Wikipedia(日本語版)Wikipedia · 2026-10-09
  2. 温泉・施設情報 - 酸ヶ湯温泉酸ヶ湯温泉株式会社 · 2026-10-09
  3. お知らせ(日帰り入浴の時間・料金、湯あみ着) - 酸ヶ湯温泉酸ヶ湯温泉株式会社 · 2026-10-09
  4. 国民保養温泉地 - 環境省環境省 · 2026-10-09
  5. アクセス - 酸ヶ湯温泉酸ヶ湯温泉株式会社 · 2026-10-09
  6. 酸ヶ湯温泉 公式サイト(トップ・休館日のお知らせ)酸ヶ湯温泉株式会社 · 2026-10-09
  7. みずうみ号(十和田北線) - JRバス東北ジェイアールバス東北 · 2026-10-09

Register sources

Data status

Name & locationPublishedCoordinatesPublishedSpring typePublishedPhotosPublishedFacilitiesPublishedVisiting info (dated)PublishedEditorial articlePublished

Updated 2026-10-09

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