A relay device wherein power can be supplied to a load from at least two power storage units and can detect when an abnormality such as an open-circuit failure occurs in a path of one of the power storage units, accurately. A control unit in a relay device functions as a switching control unit, if the current value becomes lower than a current threshold value in a first conduction path and a second conduction path, the control device switches a relay unit to an OFF state. Furthermore, the control unit functions as a determination unit and determines whether, if it switches one of the relay units to the OFF state, a voltage value detected by a voltage detection unit provided in the path in which the relay unit that was switched to the OFF state is lower than a predetermined voltage threshold value.