A hot water supply system (10) is provided which includes a first refrigerant circuit (20), an intermediate temperature water circuit (40), a second refrigerant circuit (60), and a high temperature water circuit (80). The first refrigerant circuit (20) constitutes a heat pump which uses the outdoor air as a heat source, and heats heat transfer water in the intermediate temperature water circuit (40). In the intermediate temperature water circuit (40), the heat transfer water is circulated between a radiator (45) for floor heating and a first heat exchanger (30) and between a second heat exchanger (50) and the first heat exchanger (30). The second refrigerant circuit (60) constitutes a heat pump which uses the heat transfer water in the intermediate temperature water circuit (40) as a heat source, and heats water for hot water supply in the high temperature water circuit (80).