An immediate hot-water supplying system 1 includes a P hot water supply device 10 configured to heat water flowing through a first supply pipe 2, an N hot water supply device 30 configured to heat water flowing through a second supply pipe 3, a check valve 6, and a coupled controller 60 configured to, when the flow amount detected by a second flow amount sensor 34 is equal to or more than a hot-water-supply detection flow amount, perform a hot-water supply operation in which a first burner 12 or a second burner 32 is burned with a circulation pump 16 stopped, and when the flow amount detected by the second flow amount sensor 34 is less than the hot-water-supply detection flow amount, perform a circulation heat keeping operation in which the first burner 12 is burned with the circulation pump 16 activated.