PURPOSE: To ensure locking mechanism so as not to be unlocked even when an indicating member is moved.

CONSTITUTION: A locking mechanism built in a door is engaged with an engaging member in a small door in the position in which a lock member 6 is projected. The lock member 6 is retracted, and the small door is set in an unlocking position where the small door can be opened/closed. After a deliveryman opens the small door and put an article in it, he pushes a small door lock button 9. In this way, a lever member 14 is rotated via a lock lever 9a, and the lock member 6 is projected from the end face of a base 12 via a spring member 13, so that a locking position is accomplished. When the small door is closed, the lock member 6 is pushed in once, and then, is projected by means of the spring member 13 so as to be engaged with the engaging member, and as a result, the small door is locked. A kick spring 15 is arranged in the lever member 14, and the lever member 14 is energized in the unlocking position or in the locking position, so that actions are ensured.