To provide a heat source machine capable of properly generating power by a thermal power generating element so far as only one of a hot water supply operation and a heating operation is operated.

A thermal heat generating element 18 of which a high temperature side 20 is heated by a heating means 4 is disposed. A heating circuit 2 for circulating the water for heating between a heating terminal 5 and the heating means 4, and a hot water supply circuit 3 for distributing the water for hot water supply, heated by the heating means 4 to a hot water supply terminal 13, are disposed. The heating circuit 2 and the hot water supply circuit 3 are provided with elemental cooling portions 28 for cooling a low temperature side 21 of the thermal heat generating element 18 in a state that a water channel 26 for heating, of the heating circuit 2 and a water channel 27 for hot water supply, of the hot water supply circuit 3 are heat-transferrably kept into contact with each other.