PURPOSE: To facilitate closing by lowering a trunk lid from an open position to a closed position by its own weight by an actuator, by which the energizing force of a torsion spring disappears, when the trunk lid is closed.

CONSTITUTION: When a trunk lid 3 is opened by key operation, a locking mechanism is released by the opening operation of a key cylinder, and the trunk lid 3 is opened by the energizing force of a torsion spring 9. When the trunk lid 3 is closed, a first actuator 14 is operated by the closing operation of the key cylinder, and the energizing force of the spring 9 disappears and the trunk lid 3 is closed up to an imperfectly closed position by its own weight. A latch is engaged with a striker at the position and the trunk lid 3 is locked, a second actuator is worked, and the striker is moved downward. The trunk lid 3 is locked at a perfectly closed position. Accordingly, the trunk lid 3 is closed easily, and can also be locked completely.