A monitor 1 is housed inside a casing 2 attached to a vehicle ceiling 10, and a monitor locking hook 6 locks a locking hole 1c. As a lock release button 7 is pushed to release the lock, a spring 3 located on one end side of a rotation shaft 1a rotates the monitor 1 to open the monitor 1. At that time, a gear 4 located on the other end side of the rotation shaft 1a meshes with a gear dumper 5 of the casing 2 to control the rotational speed of the monitor 1. As the stopper 9 of the monitor 1 abuts against the stopper receiver 8, the rotation thereof is stopped and the posture of the monitor 1 is held by the tension of the spring 3.