Abstract: There is provided a locking device including: a locking unit capable of performing locking and unlocking operations by rotation; an upper body part in which a first connection hole is formed; a body part which is inserted into the first connection hole of the upper body part and combined with one end of the locking unit; a lower body part in which a third connection hole into which the body part is inserted from below is formed; and a locking washer which is positioned between the upper body part and the lower body part and configured to fix and combine the upper body part and the lower body part.