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Kanto · Onsen area
かまたおんせん · 蒲田温泉
Tokyo · 大田区
Official classification
Official spring-type name (as recorded)Sodium bicarbonate/chloride cold mineral spring (Kamata Onsen); Ota's black springs are classed as bicarbonate or chloride springs
Appearance & feel
Colour and feel are listed only where a source states them. They vary by day and by bath.
What makes it special
Water so black your hand disappears in it, in a neighbourhood bathhouse in Tokyo, for 600 yen.
Facilities come from the register (Wikipedia, OpenStreetMap, official sites). Those marked "natural spring unconfirmed" are listed on the basis of their name only.
| Type | Gender | Source | Bath temperature | Free-flowing | Added water | Heated | Recirculated | Disinfected |
|---|---|---|---|---|---|---|---|---|
| Indoor bath | Separate | Own source: sodium bicarbonate/chloride cold mineral spring | Unconfirmed | Unconfirmed[2] | No[2] | Yes[2] | Unconfirmed[2] | Unconfirmed[2] |
| Indoor bath | Separate | Unconfirmed | Unconfirmed | Unconfirmed[2] | Unconfirmed[2] | Unconfirmed[2] | Unconfirmed[2] | Unconfirmed[2] |
Walk from the east exit of Kamata Station (JR Keihin-Tohoku and Tokyu lines): cross the Kanpachi ring road, take the lane beside Kamata post office and turn into Demura-dori (the bathhouse gives no walking time). By bus, routes 73/74/75 from bay 1 at the east exit, four stops to Kamata-honcho. Haneda Airport is close by.
Kamata Onsen's water is a sodium bicarbonate/chloride cold mineral spring. It comes out of the ground below 25°C and is heated over a wood fire before it reaches the tubs. The colour comes from humic acid, organic matter formed as ancient seaweed and plants were buried and broke down over ages; Ota ward describes the black water as 'fossil water derived from ancient seawater'. According to Wikipedia, you can see only about 10 cm into it, and most of these springs are mildly alkaline at pH 8–9, rich in baking soda and metasilicic acid. Kamata Onsen uses the water undiluted and splits its black bath into a hot and a cooler tub. The bathhouse lists indications such as neuralgia, muscle pain, frozen shoulder, poor circulation, fatigue, cuts and burns; we make no medical claims.
Posted by Kamata Onsen: neuralgia, muscle pain, frozen shoulder, poor circulation, fatigue recovery, general health, cuts and burns
Indications are an official statement based on the water analysis, not a guarantee of treatment. They are kept separate from opinions.
| Source | Source temperature | pH | Radon | Checked |
|---|---|---|---|---|
| Kamata Onsen source | Unconfirmed | Unconfirmed | Unconfirmed | no check date |
Kamata Onsen's ground-floor bathhouse (Kamata-honcho 2-23-2) The black-water bath is split into a hot and a cooler tub; the hot side can approach 50°C on some days. The water is heated over wood and never diluted. There are also an electric bath, jet bath, cold plunge and sauna (300 yen extra).
The blackness comes from humic acid, organic matter left by ancient seaweed and plants. It is the opposite of a clear mountain spring: the character of water from beneath a city, learned through the skin.[2]
Kamata Onsen Opened in 1937 when Shima Sadakichi, a carpenter who specialised in temple-style bathhouse architecture, drilled the well. It has run for nearly ninety years with the same water and flow. Upstairs is a canteen known for its 'onsen kamameshi' rice pots.
A bathhouse that served as basic infrastructure through earthquake and post-war recovery, still working and still fed by a hot spring. 600 yen, open daily 10:00–24:00.[1][2]
Kamata, Rokugo, Ikegami, Omori and other parts of Ota ward As of January 2026 Ota ward had 17 hot-spring facilities, mostly public bathhouses, the most of any Tokyo ward. The black water is found across its coastal districts as a cold mineral spring below 25°C, heated for bathing. Kaisei-yu in Nishi-Kamata is known for a carbonated black bath.
There is no spa town here; the baths are scattered through shopping streets and housing. Start at Kamata Onsen and hop between them to compare shades of black and feel.[3][4][5]
Along the coastal districts of Ota, at Tokyo's southern edge, a pale-brown to black-brown spring water known as kuroyu is found widely and has long fed the public bathhouses. The ward describes it as water below 25°C containing metasilicic acid and bicarbonates, 'fossil water' derived from ancient seawater. The colour comes from humic acid, the breakdown product of seaweed and plants buried long ago; visibility is about 10 cm and most of it is mildly alkaline. It is a hot spring of the volcano-free plain, born in a completely different way from mountain water. As of January 2026 the ward had 17 hot-spring facilities, the most in Tokyo's 23 wards, and a national TV programme once dubbed it the 'Ota onsen district'.[4][3][2]
Kamata Onsen opened in 1937, its well drilled by Shima Sadakichi, a master carpenter trained in the ornate temple-style architecture of bathhouses. The bathhouse's own history notes that Showa-era sento were essential infrastructure for Tokyo, indispensable in rebuilding after the Great Kanto Earthquake and the war. As home baths spread and sento dwindled, Kamata Onsen adapted while keeping the same water and flow for nearly ninety years. Among the black-water baths of Kamata it is one of the best known, famous for one of Tokyo's hottest tubs, its rice-pot canteen and T-shirts with a celebrity following.[1]
Open every day 10:00–24:00. Admission is 600 yen for adults (12 and over), 200 yen for primary-school children and 100 yen for pre-schoolers; the sauna is 300 yen extra. Cash only. With no towel or soap you can still bathe with the 900-yen 'empty-handed set' (admission included); a bath towel rents for 200 yen. The black-water bath is split into hot and cooler tubs, and the hot side can approach 50°C on some days, so start with the cooler one. There are an electric bath, a jet bath, a cold plunge and saunas on both sides, with a cool-down space in the men's bath. Parents get a baby bath and chair free of charge. Runners can use it as a changing base: leave your locker key at the desk, run, and come back to soak.[2]
Ota has no spa quarter; its hot-spring bathhouses are scattered through shopping streets and residential blocks and look and cost much like any other sento. According to the ward's own feature, Kaisei-yu in Nishi-Kamata was an early adopter of a carbonated black bath and also has a black cold plunge, a fine-bubble 'silk' bath and an aquarium of goldfish set into the bath wall. Wikipedia's list runs to a dozen or more: Yu-City Kamata and Teru-no-yu toward Rokugo, Hasunuma Onsen and Sakurakan near Ikegami, and others. Shade and feel differ from one to the next, so use Kamata Onsen as your starting point and compare two or three; even the same black water has a personality at each source.[5][3]
checked 2026-10-09
"Recommended" and "open" are recorded separately. Check the season for seasonal springs.
Dec · Jan · Feb — Winter shows off the black water's lasting warmth; check New Year opening on the official site
Apr — Closed for maintenance 6–17 April 2026; check for spring closures
The house speciality upstairs: 11:30–21:00 (last orders 20:30), with an afternoon break around 14:00–18:00; irregular closing[2]
Upstairs in the bathhouseSeventeen hot-spring facilities in the ward: Kaisei-yu's carbonated black bath, Hasunuma Onsen's paler black water and more, each a different shade and feel[5][3]
Several within walking distance of Kamata StationKamata Onsen's own merchandise, said to have celebrity fans, sold at the counter[1]
In the bathhouseFrom Kamata Station's east exit, cross the ring road and walk to Kamata Onsen. Start in the cooler black tub, then try the hot side briefly once you are used to it. Afterwards, rice pots upstairs. With time to spare, compare the carbonated black bath at Kaisei-yu in Nishi-Kamata. Bring cash. It also makes a good stop on the way to or from Haneda.
The "editors' guide" above is written by the editors from sources; it is not a visitor's opinion.
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Updated 2026-10-09
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