To make it possible to supply hot water by using a heat pump and at a highly reliable initial period.

Hot water produced with a heat pump 21 is taken into a hot water storage tank 8 once and the hot water is ejected from a rinse nozzle 4 so that it may be stored in a cleaning tank 6 in terms of initial period hot water supply. This hot water supply cycle is continued until it is detected with a water level sensor in the cleaning tank 6. Since then, the aforesaid hot water supply cycle is executed by the number of turns preliminarily determined, thereby finishing the initial period hot water supply practice. During this operation, a compressor 24 is operated in a continuous mode. On one hand, a refrigerant solenoid valve is interposed in a refrigeration cycle. When a hot water supply valve is closed, or more specifically, the refrigerant solenoid valve is closed under control synchronizing with the stop of raw water supply. This construction makes it possible to protect the compressor 24 from an abnormal pressure rise in the high pressure side even though it is being operated continuously.