PURPOSE: To carry out temperature control for obtaining comfortable temperature of the washing water conforming to the temperature sensible to the user's body by setting the temperature slightly to the warmer side if the seasonal temperature is low even if the room temperature is high by making reference to the combination of the seasonal temperature of the four seasons and the temperature of the room where a heated seat is installed.

CONSTITUTION: For the purpose of setting the temperature of washing temperature calculation circuit 1, which presumes one of the four seasons based on the average temperature of a few days up to previous day, and from a room temperature judgement circuit 2, which detects the temperature of the room where a heated seat 6 provided with a washing water function is installed, by combining both circuits together is input into a washing water temperature setting circuit 3. A washing water heater 5 is energized by means of an output from a washing water temperature adjusting circuit 4 which may adjust the temperature of the washing water set by the washing water temperature setting circuit 3 to same appropriate temperature.