Provided is a compact plug door device that can be applied even to a single sliding door and further performs a plugging operation and an opening/closing operation by means of a door driving mechanism that, to the door, imparts force in the front-back direction of a vehicle. A sliding base (12) is installed in a manner so as to be slidingly movable in the direction of vehicle width with respect to a fixed base (11). The door driving mechanism (13), which moves one door (104) in the front-back direction of the vehicle via a connecting unit (19), is installed at the sliding base (12) and has an endless member (13d), a coupled driving wheel member (13c), a drive wheel member (13b), and a drive unit (13a) containing an electric motor (21). A guide unit (15) guides a shaft (14) provided to the connecting unit (19) in a manner so as to cause motion in the direction of vehicle width. In a multiplied-speed rail (16), wherein a pinion (16c) is disposed between two racks (16a, 16b), one of the racks (16b) is connected to the sliding base (12) and the other rack (16a) is connected to the door (104) side. The pinion (16c) is connected to the connecting unit (19) side.