In guide grooves formed at both side edges of a lower face of a tray and fitted to a pair of left and right guide members of a cabinet, the guide groove substantially in a U-like shape on one side is inserted with a front end portion of an elastic plate integrally projected at a front portion of the cabinet, a recess portion is formed at a portion of one side face of the guide groove 12 opposed to the elastic plate in a state of containing the tray into the cabinet, and formed such that by bringing the one side face of the guide groove 12 into elastic contact with the elastic plate opposed to the recess portion in moving the tray forward, other side face of the guide groove is brought into contact with reference guide faces of the guide member on one side to thereby prevent the tray from being inclined.