The present invention realizes a power supply device that can, even if an abnormality occurs in a power supply unit, block a current from flowing into the path from the other power supply unit. A power supply device (1) includes: a first conductive path (31) that is a path for power between a first power supply unit (91) and a load (94); a second conductive path (32) that is connected to the first conductive path (31) and to a second power supply unit (92); a first switch unit (34) that is provided on the first conductive path (31) between a connection part (33), at which the first conductive path (31) is connected to the second conductive path (32), and the first power supply unit (91), and switches to an electrically disconnected state, in which the first switch unit (34) blocks a current from flowing in either direction, and to an electrically connected state, in which the first switch unit (34) allows a current to flow therethrough; a second switch unit (35) that is provided on the second conductive path (32) between the connection part (33) and the second power supply unit (92), and switches to an electrically disconnected state, in which the second switch unit (35) blocks a current from flowing in either direction, and to an electrically connected state, in which the second switch unit (35) allows a current to flow therethrough; and a control unit (39) that controls respective switching operations of the first switch unit (34) and the second switch unit (35).