A movable unit (50) is disposed between a loaded recording medium (1) and a bottom surface (4a) of a base chassis (4) opposite to the surface of the loaded recording medium (1). The movable unit includes a spindle motor (53), a head (51), guide shafts (52a, 52b) for supporting the head (51) movably in a radius direction of the recording medium (1), and a movable holding device (5), disposed at the base chassis (4) swingable downward to the bottom surface (4a), for holding the spindle motor (53), the head (51) and the guide shafts (52a, 52b). The movable holding device (5) holds at least one of the spindle motor (53), the head (51) and the guide shafts (52a, 52b) movably in a direction moving away from the bottom surface (4a) relative to the movable holding device (5). A limiting device (60a, 60b) is disposed between the movable unit (50) and the bottom surface (4a) for limiting a movable range of the movable unit (50), so that at least a part of the movable unit (50) is maintained with a distance apart from the bottom surface (4a), even if the movable holding device (5) swings down.