The invention relates to a heat radiation member and a cabinet to be installed outdoors in a hermetic state, having a heat radiation function for heat radiation of devices contained therein. The object of the invention is to facilitate maintenance, downsize the cabinet, and prevent occurrence of noise. It includes: a cabinet body containing a heat source; a cover member attached to an aperture of the cabinet and having a guide portion guiding, to an exterior of the cabinet, a heat transfer member for transferring therethrough heat from the heat source by use of a hydraulic fluid; and a heat radiation part being a thermal conductor and in contact with the heat transfer member on a face and covering the heat transfer member from the exterior of the cabinet and having a heat radiation member on a face opposite to the face in contact with the heat transfer member.