A DC/DC converter 10 of the present invention is provided with a constant-voltage power supply circuit 11; a SENSE+ terminal; a SENSE−/OCPSEL terminal pulled up to a predetermined voltage VL through a pull-up resistor R8; and a controller 14 for controlling the constant-voltage power supply circuit 11, wherein the controller 14 controls the output voltage Vout of the constant-voltage power supply circuit 11 on the basis of a potential difference between the SENSE+ terminal and the SENSE−/OCPSEL terminal, on the condition that the voltage of the SENSE−/OCPSEL terminal is lower than a threshold voltage, and sets predetermined control parameters on the basis of the voltage of the SENSE−/OCPSEL terminal, on the condition that the voltage of the SENSE−/OCPSEL terminal is equal to or higher than the threshold voltage.