An apparatus is provided in which a motor 11 with reduction gears, a clutch 12 and a gas stay are provided between a vehicle body 2 and a tailgate 1 so that a fully opened position of the tailgate can be held by virtue of a thrust of the gas stay only, and in this apparatus, when a closure of the tailgate from its own weight is detected after the motor with reduction gears is disconnected, the motor with reduction gears is connected to the tailgate to drive to forcibly close it after the tailgate is driven to be opened to the fully opened position thereof. By this construction, when the holding force of the opened position is short, since the tailgate is closed after it is opened to the fully opened position once, cargo loading and unloading work can be completed while the tailgate is so closed.