A latch is disposed turnably on a side door and becomes in a state of engaging with a striker disposed on a vehicle body. A ratchet engages with the latch by an engaging operation, and releases the engaging state by a disengaging operation. An open lever performs a door opening operation by the opening operation of an operating handle. A lever member is in contact with the latch in the engaging state, and excessively oscillates the latch in the direction of a closing operation, by which the engaging state between the latch and the ratchet is released during the time from the opening operation of the operating handle to the disengaging operation of the ratchet.