Provided is a technology in which a control device of a converter performs gate cutoff for cutting off power supply to a load when one of a battery detection value obtained by a battery voltage sensor or a low-voltage-side detection value obtained by a low-voltage-side voltage sensor or both thereof are abnormal values. After the control device performs the gate cutoff, the control device determines whether or not a main body circuitry is abnormal based on the battery detection value and the low-voltage-side detection value. When the control device determines that the main body circuitry is not abnormal, the control device determines whether one of the battery voltage sensor or the low-voltage-side voltage sensor is abnormal based on the battery detection value, the low-voltage-side detection value, and a high-voltage-side detection value obtained by a high-voltage-side voltage sensor.