Provided is a mobile X-ray apparatus that is capable of safely charging multiple mobile X-ray apparatuses. A power supply device 10 includes a plug 7; an electrical outlet 8; a battery 12; a control unit 20; a current detector 26; and a power supply circuit 30. The power supply circuit 30 includes a power limiting circuit 40; an external output circuit 50; and a charging circuit 60. The power limiting circuit 40 limits power together with the control unit 20. In the power supply circuit 30, i) if an external output circuit 50 side is current-limited, charging is preferentially performed, and ii) if the charging circuit 60 side is current-limited, power is output preferentially to external equipment. In the power supply circuit 30, the current of one current path is limited, and a large amount of current is allowed to flow preferentially in the other current path.