Disclosed are a heater and hot water supplying device having the same. A temperature stabilizing unit is formed by arranging an inlet and an outlet of a water container close to each other. Under this configuration, cool water introduced into a water path of the water container via the inlet serves to cool hot water to be discharged via the outlet of the water container. This may prevent the hot water from being overheated to temperature more than a preset value. As a result, this may prevent damage of thermal lines of a heating element, due to overheating, the overheating occurring as water inside the water container is overheated.