An underwater power supply system configured to supply electrical power underwater to one or a plurality of underwater moving bodies, the underwater moving body having a first rechargeable battery, a first power-receiving coil, and a moving device by which the underwater moving body may move underwater, the system comprising: an ascending/descending station that has: a second rechargeable battery; a second power-receiving coil; a second power-supplying coil; a main body which accommodates the second rechargeable battery, the second power-receiving coil, and the second power-supplying coil; and an ascending/descending apparatus configured to cause the main body to ascend and descend underwater between a water depth at which the underwater moving body works and the vicinity of the water surface; and characterised in that it comprises: a charging station that is either installed on-land or is positioned on the water surface, is connected to an external electrical power supply, and_has a first power-supplying coil, the charging station being configured to supply electrical power wirelessly via the first power-supplying coil and the second power-receiving coil to the ascending/descending station in the vicinity of the water surface to charge the second rechargeable battery, wherein, at the water depth, when the underwater moving body moves adjacent to the ascending/descending station, electrical power is supplied wirelessly from the ascending/descending station via the second power-supplying coil and the first power-receiving coil to the underwater moving body to charge the first rechargeable battery. an ascending/descending station that has: a second rechargeable battery; a second power-receiving coil; a second power-supplying coil; a main body which accommodates the second rechargeable battery, the second power-receiving coil, and the second power-supplying coil; and an ascending/descending apparatus configured to cause the main body to ascend and descend underwater between a water depth at which the underwater moving body works and the vicinity of the water surface; and characterised in that it comprises: a charging station that is either installed on-land or is positioned on the water surface, is connected to an external electrical power supply, and_has a first power-supplying coil, the charging station being configured to supply electrical power wirelessly via the first power-supplying coil and the second power-receiving coil to the ascending/descending station in the vicinity of the water surface to charge the second rechargeable battery, wherein, at the water depth, when the underwater moving body moves adjacent to the ascending/descending station, electrical power is supplied wirelessly from the ascending/descending station via the second power-supplying coil and the first power-receiving coil to the underwater moving body to charge the first rechargeable battery. a charging station that is either installed on-land or is positioned on the water surface, is connected to an external electrical power supply, and_has a first power-supplying coil, the charging station being configured to supply electrical power wirelessly via the first power-supplying coil and the second power-receiving coil to the ascending/descending station in the vicinity of the water surface to charge the second rechargeable battery, wherein, at the water depth, when the underwater moving body moves adjacent to the ascending/descending station, electrical power is supplied wirelessly from the ascending/descending station via the second power-supplying coil and the first power-receiving coil to the underwater moving body to charge the first rechargeable battery.