The invention provides a lock mechanism which can effectively use driving current supplied to driving source to reduce the operating physical force required for the opening operation of operating handle with lower cost and miniaturized device. A latch mechanism holds a door body in a half-closed state or a fully-closed state with respect to a vehicle body. An open lever connected to an operating handle on the door body releases the half-closed state or the fully-closed state. A release assisting unit triggered by the opening operation of the operating handle assists the release of the half-closed state or the fully-closed state of the door body. A charging device charges a portion of a driving current supplied to a driving source of a lock mechanism between the operating handle and the latch mechanism, and supplies a charged driving current to the release assisting unit.