HEAT SOURCE DEVICE

PROBLEM TO BE SOLVED: To reduce waste of heat energy in the operation during quick reheating when a thermal insulation mode of a bath tub warm water operates.SOLUTION: The liquid circulation channel 5 for heating for circulating liquid through a heating device and a reheating circulation channel 13 connected to the bath tub are thermally connected via the liquid-liquid heat exchanger 7, the liquid in the liquid circulation channel 5 for heating is circulated while being heated by the heat exchanger 28 for heating, the warm water in the bath tub is circulated through the reheating circulation channel 13, thereby the reheating operation of the warm water in the bath tub is carried out. The bypass channel 43 for circulating the liquid in the liquid circulation channel 5 for heating not passing the same through the cistern unit 100 is installed, the circulation channel of the liquid in the liquid circulation channel 5 for heating is circulated not through the cistern unit 100 but through the bypass channel 43 during the quick reheating operation carried up when a temperature difference between the temperature when starting to heat the warm water in the bath tub and a bath set temperature is not more than a set temperature determined in advance.