A water heating apparatus, comprising: a heat source circuit including a first circulation pump, a heat pump, and a heat source side of a hot water supply tank heat exchanger that are connected to each other by a pipe, the heat source circuit being configured to allow water to circulate therethrough; a hot water supply circuit including a second circulation pump, a use side of the hot water supply tank heat exchanger, and a hot water supply tank that are connected to each other by a pipe, the hot water supply circuit being configured to allow water to circulate therethrough; characterized in that a control unit comprises: means for comparing a water temperature in the hot water supply tank and a reheating tank temperature with each other; and means for performing, when the water temperature in the hot water supply tank falls below the reheating tank temperature, reheating so that the water temperature in the hot water supply tank becomes a target tank temperature, and the contol unit being configured to control a flow rate of the second circulation pump based on change in temperature in the hot water supply tank; wherein the control unit is further configured to: control, when it is determined that the change in temperature is a predetermined first reference value or more, the flow rate of the second circulation pump to a minimum in an operation allowable range; and control, when it is determined that the change in temperature is less than a predetermined second reference value, the flow rate of the second circulation pump to a maximum in the operation allowable range. a heat source circuit including a first circulation pump, a heat pump, and a heat source side of a hot water supply tank heat exchanger that are connected to each other by a pipe, the heat source circuit being configured to allow water to circulate therethrough; a hot water supply circuit including a second circulation pump, a use side of the hot water supply tank heat exchanger, and a hot water supply tank that are connected to each other by a pipe, the hot water supply circuit being configured to allow water to circulate therethrough; characterized in that a control unit comprises: means for comparing a water temperature in the hot water supply tank and a reheating tank temperature with each other; and means for performing, when the water temperature in the hot water supply tank falls below the reheating tank temperature, reheating so that the water temperature in the hot water supply tank becomes a target tank temperature, and the contol unit being configured to control a flow rate of the second circulation pump based on change in temperature in the hot water supply tank; wherein the control unit is further configured to: control, when it is determined that the change in temperature is a predetermined first reference value or more, the flow rate of the second circulation pump to a minimum in an operation allowable range; and control, when it is determined that the change in temperature is less than a predetermined second reference value, the flow rate of the second circulation pump to a maximum in the operation allowable range. means for comparing a water temperature in the hot water supply tank and a reheating tank temperature with each other; and means for performing, when the water temperature in the hot water supply tank falls below the reheating tank temperature, reheating so that the water temperature in the hot water supply tank becomes a target tank temperature, and the contol unit being configured to control a flow rate of the second circulation pump based on change in temperature in the hot water supply tank; wherein the control unit is further configured to: control, when it is determined that the change in temperature is a predetermined first reference value or more, the flow rate of the second circulation pump to a minimum in an operation allowable range; and control, when it is determined that the change in temperature is less than a predetermined second reference value, the flow rate of the second circulation pump to a maximum in the operation allowable range. control, when it is determined that the change in temperature is a predetermined first reference value or more, the flow rate of the second circulation pump to a minimum in an operation allowable range; and control, when it is determined that the change in temperature is less than a predetermined second reference value, the flow rate of the second circulation pump to a maximum in the operation allowable range.