PURPOSE: To surely engage a restraining member with the restrained part of a cassette even when the cassette is ejected more than a spcecified amount.

CONSTITUTION: By a carrying means a sliding lug 84 engaged/disengaged with a hidden hole 94 installed on a cassette 10 is moved in forward and backward directions, the cassette 10 is taken in to the inside or pushed out from the inside, the sliding lug 84 is rotated in the forward and backward directions on a specidied position and engaged/disengaged with the hidden hole 94 of the cassette 10. The sliding lug 84 provided on the rotative edge part of a rotative arm 115 is rotated along the cassette 10 when it is detached from the hidden hole 94 of the cassette 10 and thus, a bearing 112 is engaged with the hidden hole 94 of the cassette 10 where the sliding lug 84 is ejected from an optical disk device. At this time, when the cassette 10 is ejected more than a specified amount, the rotative arm 115 is rotated against a pressing force, retreated and the sliding lug 84 is engaged with the hidden hole 94 of the cassette 10 by bringing it into contact with the cassette 10.