A plug door device (1; 2) to be installed at an entrance (102; 106) of a vehicle for performing an operation of opening and closing a door (104; 108, 109) and a plugging operation of moving the door (104; 108, 109) in a vehicle width direction, comprising: a) a fixed base (11; 51) that is fixed to a body of the vehicle; b) a slide base (12; 52) installed on the fixed base (11; 51) slidably relative to the fixed base (11; 51) in the vehicle width direction; c) a door drive mechanism (13; 53) that is installed on the slide base (12; 52) and moves the door (104; 108, 109) in a vehicle front-rear direction via a connecting portion (19; 59); d) a shaft portion (14; 54) provided on the door (104; 108, 109) or the connecting portion (19; 59); e) a guide portion (15; 55) that is rotatably installed on the fixed base (11; 51), pivots while abutting the shaft portion (14; 54) and guides the shaft portion (14; 54) such that the shaft portion (14; 54) moves toward one side in the vehicle width direction when the door (104; 108, 109) opens, and pivots while abutting the shaft portion (14; 54) and guides the shaft portion (14; 54) such that the shaft portion (14; 54) moves toward another side in the vehicle width direction when the door (104; 108, 109) closes; f) a double-speed rail (16; 56) that has two facing racks (16a, 16b) and a pinion disposed between the two racks (16a, 16b), the two racks (16a, 16b) being installed so as to extend in the vehicle front-rear direction, one of the two racks (16a, 16b) being connected to the slide base (12; 52) and the other one thereof being connected to the door (104; 108, 109), and the pinion being connected to the connecting portion (19; 59); and g) a locking mechanism (17; 57) capable of locking the door (104; 108, 109) so as to restrict a movement of the door (104; 108, 109) at a closed position of the door (104; 108, 109), wherein the locking mechanism (17; 57) include: h) a fixed lock portion (36; 62) provided so as to be fixed on the fixed base (11; 51); and i) a movable lock portion that is provided movably with the driving force that is output from a planet gear of the door drive mechanism (13; 53) to the locking mechanism (17; 57), and comes into contact with the fixed lock portion (36; 62) on the inside in the vehicle width direction at the closed position of the door (104; 108, 109), j) a movement of the door (104; 108, 109) outward in the vehicle width direction is restricted when the door (104; 108, 109) is in a closed state; wherein the movable lock portion includes: k1) a sliding contact portion capable of coming into contact with the fixed lock portion (36; 62); k2) a slide rail that is fixed to the slide base and restricts a sliding direction of the sliding contact portion; and k3) a transmission member that transmits a driving force that is output from the planet gear of the door drive mechanism (13; 53) to the locking mechanism (17; 57) to the sliding contact portion. a) a fixed base (11; 51) that is fixed to a body of the vehicle; b) a slide base (12; 52) installed on the fixed base (11; 51) slidably relative to the fixed base (11; 51) in the vehicle width direction; c) a door drive mechanism (13; 53) that is installed on the slide base (12; 52) and moves the door (104; 108, 109) in a vehicle front-rear direction via a connecting portion (19; 59); d) a shaft portion (14; 54) provided on the door (104; 108, 109) or the connecting portion (19; 59); e) a guide portion (15; 55) that is rotatably installed on the fixed base (11; 51), pivots while abutting the shaft portion (14; 54) and guides the shaft portion (14; 54) such that the shaft portion (14; 54) moves toward one side in the vehicle width direction when the door (104; 108, 109) opens, and pivots while abutting the shaft portion (14; 54) and guides the shaft portion (14; 54) such that the shaft portion (14; 54) moves toward another side in the vehicle width direction when the door (104; 108, 109) closes; f) a double-speed rail (16; 56) that has two facing racks (16a, 16b) and a pinion disposed between the two racks (16a, 16b), the two racks (16a, 16b) being installed so as to extend in the vehicle front-rear direction, one of the two racks (16a, 16b) being connected to the slide base (12; 52) and the other one thereof being connected to the door (104; 108, 109), and the pinion being connected to the connecting portion (19; 59); and g) a locking mechanism (17; 57) capable of locking the door (104; 108, 109) so as to restrict a movement of the door (104; 108, 109) at a closed position of the door (104; 108, 109), h) a fixed lock portion (36; 62) provided so as to be fixed on the fixed base (11; 51); and i) a movable lock portion that is provided movably with the driving force that is output from a planet gear of the door drive mechanism (13; 53) to the locking mechanism (17; 57), and comes into contact with the fixed lock portion (36; 62) on the inside in the vehicle width direction at the closed position of the door (104; 108, 109), j) a movement of the door (104; 108, 109) outward in the vehicle width direction is restricted when the door (104; 108, 109) is in a closed state; k1) a sliding contact portion capable of coming into contact with the fixed lock portion (36; 62); k2) a slide rail that is fixed to the slide base and restricts a sliding direction of the sliding contact portion; and k3) a transmission member that transmits a driving force that is output from the planet gear of the door drive mechanism (13; 53) to the locking mechanism (17; 57) to the sliding contact portion.