PURPOSE: To enhance the convenience accompanied by operations which start and stop water supply, and change over hot water to cold water and vise versa.

CONSTITUTION: There is installed a hot water supply control 17 which selects OFF mode which stops water supply (hot water supply), hot water mode which lets hot water to flow out, and water mode which lets water to flow out on a side of a shower head 11. A microcomputer 18 controls the power supply for a water solenoid valve 8, a gas solenoid valve 14, and a sparker 12. The output and transmission method for an operation signal are carried out by a light emitting device 19 and a light receiving device 20 and a light receiving device 20 laid out in a water boiler case 4 and a prism built-in with a slide switch which interlocks with the control 17, and two sets of flood lighting optical fiber 23 and 24 and light receiving optical fiber 25 and 26.