A hot-water supply system 1 comprises a temperature responsive valve 61 provided in a first bypass passage 60, an orifice 31 provided in a second bypass passage 30, a flow rate sensor 24 provided in a water supply passage 11 downstream from a connection point with the second bypass passage 30, a circulating pump 33 provided in the water supply passage 11 downstream from the connection point with the second bypass passage 30, and a controller 4. The controller 40 operates the circulating pump 33 and executes circulation heating operation for operating a burner to heat the hot water circulating through a circulation circuit 80, when a flow rate detected by the flow rate sensor 24 is equal to or more than a specified flow rate.