PURPOSE: To obtain hot water with set temperature in a short time by a method wherein hot water is discharged under the condition that feed water is throttled at the start of the use of the hot water supplier or when the deviation between the feed water temperature and the set value of hot water temperature is changed and feed water is increased when the deviation between the hot water temperature and the set value of hot water temperature attains to the predetermined value.

CONSTITUTION: In the hot water supplier to obtain hot water by heating the water passing through a heat exchanger 2 with the heat of combustion produced at a gas burner 1, a feed water temperature detector 8 and a discharging hot water temperature detector 4 are arranged respectively at the inlet side and at the outlet side of the heat exchanger 2. The outputs of the respective detectors 8 and 4 are inputted to the controlling device 7 in order to obtain the deviations from the set signals of the respective hot water temperature setter 5. After that, required combustion rate is determined from the deviation between the discharging hot water temperature and the set value of hot water temperature in order to control a controller 6 of heat quantity to be supplied. In addition, a controller 9 of feed water flow is controlled up to the feed water flow controllable from the deviation between the feed water temperature and the set value of hot water temperature. Consequently, the desired hot water temperature can be obtained in a short time, resulting in enabling to improve the practicability of the hot water supplier.