PURPOSE: To provide a hot water supply device which can easily be handled so as to change the volume of hot water supply in accordance with a degree of depression of a push button.

CONSTITUTION: An inductance changing member 14 composed of a bottomed metal column, press-fitted around the outer periphery of the lower part of a resin molded push-button 10, is provided in a casing 13 so as to be vertically slidable. Further, a spring 15 is located underneath the push-button 10. A detecting coil 16 is laid around the position where the push-button is pressed in. When the inductance changing member 14 is inserted into the detecting coil 16, the inductance varies so that the resonance point deviates, and accordingly, the potential lowers. Thus, this signal is applied to a motor for a motor-drive pump.