A mold clamping device in an injection molding machine comprising a stationary electromagnetic plate and a movable electromagnetic plate provided at the side of the stationary electromagnetic plate away from the movable platen so as to be capable of being moved toward and away from the stationary electromagnetic plate. Both electromagnetic plates are each provided with an electromagnetic coil for generating a magnetic attracting force. The device further comprises a movable platen driving mechanism which is composed of a combination of a feed screw shaft and a nut member and is connected to the movable platen. An operation for closing the molds is performed by the driving mechanism. Subsequently, a mold clamping operation of both molds is performed by a magnetic attracting force from the electromagnetic coil.