The purpose of the present invention is to implement a power conversion device capable of suppressing the reverse flow of current and improving current responsiveness and power conversion efficiency.A snubber capacitor (25) capable of absorbing switching surge is connected to a low voltage-side switching circuit having switching elements (250, 260, 270, and 280). It is determined that the snubbercapacitor (25) is not fully charged or has not approached a fully charged state until a predetermined time elapses since the start of switching was requested to a control device 310, and control is made such that the low voltage-side switching circuit and a high voltage-side switching circuit that has switching elements (210, 220, 230, and 240) are asynchronous. After the predetermined time has elapsed, control is made such that the low voltage-side switching circuit and the high voltage-side switching circuit are synchronous, and duty ratios of the low voltage-side switching circuit and thehigh voltage-side switching circuit are controlled such that current does not flow reversely from the low voltage-side switching circuit to the high voltage-side switching circuit.