PURPOSE: To provide the cleaning device for bathtub hot water capable of detecting a waterless state when a circulating pump runs idle by a simple mechanism free from malfunctions.

CONSTITUTION: The circulating pump 15 and/or a heater tank 16 are formed as a tank 10 for detection of the absence of the water. This tank is equipped with a tank weight detector 11 having a weight detecting element such as, for example, a pressure sensitive element. The reference weight previously stored in a storage device 13 and a detected weight are compared by a controller 12 and the absence of water is discriminated when the detected weight is below the reference weight. Then the detection of the absence of the water is exact without malfunctions. The energization to the circulating pump 15 and the heater tank 16 is immediately stopped when the absence of the water is discriminated. The safety of the device is thus enhanced.