A plug door device comprising: a stationary base fixedly attached to a body of a vehicle; a slidable base having a door attached thereto to open or close a doorway of the vehicle, the slidable base being movable in a width direction of the vehicle relative to the stationary base when acted upon by a driving force from a drive source; and a restricting mechanism for restricting the slidable base from moving in the width direction when the door is fully closed, wherein the restricting mechanism includes: two stationary members fixedly attached to the stationary base, the stationary members each having a restricting part; two movable members attached to two portions of the slidable base that are separate from each other in a front-rear direction of the vehicle, the two movable members respectively pairing up with the two stationary members; and a connecting shaft connecting together the two movable members, wherein, when the door is fully closed, the two movable members connected together via the connecting shaft touch the restricting parts, so that an external force causes the movable members to unitedly move toward restriction areas where the slidable base is restricted from moving in the width direction, wherein the restricting parts are recesses formed in the stationary members and depressed toward one of the sides in the front-rear direction, wherein the two movable members each have a projecting part configured to, when the door is fully closed, fit in the recess under influence of the external force, wherein each stationary member has an opening extending through the stationary member in a height direction of the vehicle, characterized in that the opening is divided into a restriction area, corresponding to the recess, and a non-restriction area where the slidable base is allowed to move in the width direction, and wherein the opening is shaped like an L when seen in the height direction. a stationary base fixedly attached to a body of a vehicle; a slidable base having a door attached thereto to open or close a doorway of the vehicle, the slidable base being movable in a width direction of the vehicle relative to the stationary base when acted upon by a driving force from a drive source; and a restricting mechanism for restricting the slidable base from moving in the width direction when the door is fully closed, wherein the restricting mechanism includes: two stationary members fixedly attached to the stationary base, the stationary members each having a restricting part; two movable members attached to two portions of the slidable base that are separate from each other in a front-rear direction of the vehicle, the two movable members respectively pairing up with the two stationary members; and a connecting shaft connecting together the two movable members, two stationary members fixedly attached to the stationary base, the stationary members each having a restricting part; two movable members attached to two portions of the slidable base that are separate from each other in a front-rear direction of the vehicle, the two movable members respectively pairing up with the two stationary members; and a connecting shaft connecting together the two movable members, wherein, when the door is fully closed, the two movable members connected together via the connecting shaft touch the restricting parts, so that an external force causes the movable members to unitedly move toward restriction areas where the slidable base is restricted from moving in the width direction, wherein the restricting parts are recesses formed in the stationary members and depressed toward one of the sides in the front-rear direction, wherein the two movable members each have a projecting part configured to, when the door is fully closed, fit in the recess under influence of the external force, wherein each stationary member has an opening extending through the stationary member in a height direction of the vehicle, characterized in that the opening is divided into a restriction area, corresponding to the recess, and a non-restriction area where the slidable base is allowed to move in the width direction, and wherein the opening is shaped like an L when seen in the height direction.