An object is to provide an output-noise reduction device that can prevent noise from an electronic device accommodated in a metal casing from being transmitted due to electromagnetic coupling. An output voltage is extracted to the outside through a conducting bar. A magnetic body core includes a through hole through which the conducting bar is inserted. A chip capacitor is mounted on a mounting board and connects between the output terminal VO and ground potential. A section from the output terminal VO to at least part of the chip capacitor mounted on the mounting board is isolated from the electromagnetic coupling from the electronic device. Thus, noise is prevented from being transmitted to the output terminal VO.