To enable an accurate sensing of taking a bath to be carried out even during a purifying or cleaning operation at a bath device.

There is provided a bath device 2 capable of performing a purifying or cleaning operation for filtering bath tub water while circulating it between a bathtub 1 and a circulation passage 3. As to an action of a person taking a bath for the bathtub 1, it is not checked by a water level sensor 21 as found in the prior art example, but it is checked by a degree of descending of a temperature of a bathtub water. With such an arrangement as above, a presence or a non-presence of sensing a person taking a bath can be acknowledged accurately even during a purifying or cleaning operation to drive a circulation pump 4 without temporarily stopping or interrupting an operation of the circulation pump 4.