To provide a hot water generating device for discriminating whether a flow switch is broken down or not.

A hot water ejection pipe 5 and a cold water intake pipe 4 of a heat exchanger 1 are connected through a circulation pipe 40. The flow switch 36 provided with a flow state display section is disposed on the cold water intake pipe 4. A solenoid valve 41 for being manually opened and closed is disposed in the circulation pipe 40 as an operation valve, and a flow monitor 44 for monitoring the flow in the circulation pipe 40, is disposed in the circulation pipe 40. When the flow switch 36 comprising the flow state display section, displays the detection of flowing-down of cold water, the manually-openable and closable solenoid valve 41 as the operation valve of the circulation pipe 40 is opened, and the flow in the circulation pipe 40 is monitored through the flow monitor 44 to confirm existence or nonexistence of flow, thus it is discriminated that the flow switch 36 is normal when the flow exists, and the flow switch 36 is broken down when the flow does not exist.