Provided is a small plug door device having a slide base is installed slidably in a vehicle width direction relative to a fixed base. A door drive mechanism for moving one door in a vehicle front-rear direction via a connecting portion has a drive portion including an electric motor, a drive wheel member, a follower wheel member, and an endless member, and is installed on the slide base. A guide portion guides a shaft portion provided on the connecting portion so as to move the shaft portion in a vehicle width direction. In a double-speed rail in which a pinion is disposed between two racks, one rack is connected to the slide base, the other rack is connected to the door side, and the pinion is connected to the connecting portion.