PURPOSE: To obtain a water heater having improved utility of switching use of hot/cold water by conducting the opening and closing of a water tap mechanically when cold water alone is used.

CONSTITUTION: When a hot water temperature regulating lever 56 is set at a 'cold water' position, a hot water temperature regulating dial member 138 rotates and a hot/cold water switchover operation piece 142 provided for this hot water temperature regulating dial member 138 pushes down a water tap opening-closing lever 108, so as to open a water tap 20. At the same time, a hot/cold water switchover switch operating piece 144 turns a hot/cold water switchover switch 58 ON so as not to make a gas burner ignited. According to this constitution, the use of cold water alone can be attained by a one-touch operation.