To provide a mist sauna device which prevents contamination of water supply caused by backflow and excessive rise of internal pressure of a channel for spraying, which can be easily installed as drain pipes are removed and which is compact.

A first electromagnetic valve 10 is provided at a channel 7 for spraying on the upstream side of a fluid-fluid heat exchanger 11. A second electromagnetic valve 12 is provided at the channel 7 for spraying on the downstream side of the fluid-fluid heat exchanger 11. At the channel for spraying on the upstream side of the first electromagnetic valve 10, a check valve 9 is provided for allowing the flow of water directed toward the first electromagnetic valve 10 and for preventing backflow directed from the first electromagnetic valve 10 toward the upstream direction. A first overpressure escaping means 20 is provided for escaping internal pressure of the channel 7 for spraying between the first electromagnetic valve 10 and the check valve 9 when the first electromagnetic valve 10 is closed. A second overpressure escaping means 22 is provided for escaping internal pressure of the channel 7 for spraying between the first electromagnetic valve 10 and the second electromagnetic valve 12 when both the first electromagnetic valve 10 and the second electromagnetic valve 12 are closed.