A front mechanism mounted on a chassis loads a cassette in place by causing a first projection and a second projection on each of opposite side portions of a cassette carrying tray to slide along respective guide grooves formed in each of side plates. Power is transmitted from a drive cam gear provided on the rear side of the chassis to the tray via a drive mechanism, intermediate gear and rotary gear. For loading, the tray initially starts to move as inclined with the first projection and the second projection sliding along slanting grooves and is thereafter lowered by sliding movement of the projection along a vertical groove and sliding movement of the projection along a descent groove while being corrected from the inclined position to a horizontal position. Upon completion of cassette loading, the intermediate gear and the rotary gear constitute a Geneva stop, and the drive cam gear disengages from the drive mechanism. A support guide supporting the drive mechanism is provided by being formed by outsert molding inside the chassis and thereafter being rotated to project from a side portion of the chassis.