Right Onsen › Gunma › Tomioka
Oshima Kosen
4.2★ · 165 Google ratings · Tomioka, Gunma · 大島鉱泉
✓ Day visitors
Before you go
Can you bathe here?
Day visitors
✓ YesConfirmed by recent visitor reports
Hours
13:00–19:00From the facility's listing
Tattoos
? Call aheadNo policy stated in the 42 recent reviews we read or on the facility's website
Price
¥450 adultConfirmed by recent visitor reports
Bathing
Men and women separateReported by two visitors
How we know this
- Day visitors: Open to walk-in day visitors for a flat admission fee, with no residency or membership requirement mentioned. · 3 visitors, Apr 2025 – Jul 2026
- Price: Ten separate reviewers confirm the entry fee is a flat 450 yen for adults. · 10 visitors, Dec 2024 – Jul 2026
- Bathing arrangement: Men's and women's baths are separate, though the women's side has occasionally needed to be prepared on the spot for low demand. · 2 visitors, Mar 2026 – Aug 2026
The bath
What you’ll find
A century-old, tiny indoor mineral-spring (kosen) bathhouse in rural Tomioka, Gunma, with one small tub, basket-only changing room, and 450 yen cash entry, run across four generations of the same family, day-use only since it stopped offering lodging during COVID.
Bath setup
Indoor baths
1.0Reported by one visitor
Cold bath
✕ NoReported by one visitor
Spring water
Spring type
mineral springConfirmed by recent visitor reports
pH
pH 8Reported by one visitor
Heated
✓ YesReported by two visitors
How we know this
- Indoor baths: One review describes a single fairly-sized tub with four washing stations. · 1 visitor, Mar 2026
- Cold bath: No cold plunge bath is present; the single tub itself runs hot. · 1 visitor, Mar 2026
- Spring type: Described as Gunma's only kosen (unheated mineral spring), with distinctly yellow-tinted water. · 3 visitors, Apr 2025 – Jul 2026
- pH: One reviewer measured the water at roughly pH 8. · 1 visitor, Mar 2026
- Heated: Because the source is a cold spring, the water is heated with a firewood stove before bathing. · 2 visitors, Apr 2025 – Sep 2025
Practical
What you need
Soap & shampoo
✓ ProvidedConfirmed by recent visitor reports
Hair dryer
✓ YesConfirmed by recent visitor reports
Facilities
Lodging
✕ NoOvernight lodging used to be offered but was discontinued because of COVID.Reported by two visitors
How we know this
- Soap & shampoo: Most reviewers confirm shampoo and bar soap are provided, though one visitor advised bringing your own toiletries just in case. · 5 visitors, Dec 2024 – Jul 2026
- Hair dryer: A hair dryer is available, though one reviewer found it barely functional. · 3 visitors, Sep 2025 – Nov 2025
- Lodging: Overnight lodging used to be offered but was discontinued because of COVID. · 2 visitors, Sep 2025 – Jun 2026
Timing
When to go
Weekly hours
| Day | Hours |
|---|---|
| Monday | 13:00–19:00 |
| Tuesday | 13:00–19:00 |
| Wednesday | 13:00–19:00 |
| Thursday | 13:00–19:00 |
| Friday | 13:00–19:00 |
| Saturday | 13:00–19:00 |
| Sunday | 13:00–19:00 |
Getting there
How to get there
Nearest station
Joshu-IchinomiyaAbout 21 min on foot, 1.7 km in a straight line
Address
148 Oshima, Tomioka, Gunma 370-2335From the facility's listing
Show a driver
大島鉱泉The name in Japanese, for a taxi or at the counter
Phone
+81274-62-1490Japanese-speaking. For tattoos or private baths a call is the only sure answer
Website
www.tomioka-silk.jpOfficial, in Japanese
The map loads only when you ask for it and connects your browser to Google.
Nearby
Other baths close by
Myōgi Fureai Plaza / Myōgi Onsen Hot Spring ‘Momiji no Yu’
3.9★ · 10.8 km
✓Day useTattoos ?✓Outdoor bath✓Sauna
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Questions
Common questions
Can I visit Oshima Kosen without staying overnight?
Open to walk-in day visitors for a flat admission fee, with no residency or membership requirement mentioned.
How much does Oshima Kosen cost?
Ten separate reviewers confirm the entry fee is a flat 450 yen for adults.
