To provide a bi-part sliding type platform door device having no lintel in the over-part as improvement of a conventional arrangement based on the bi-part sliding system in which when the left and right door pieces are shut, it may happen that any door inclines to the vehicle side or to the opposite side in its forefront away from the door pocket even if the part near the door pocket is in the vertical attitude approximately.

The tip of a movable shaft installed on one of the doors and capable of moving in the horizontal direction relative to the door is attached to a link, and the other end of the link is attached to a key, which is arranged moving to the left and right in compliance with the left-right motions of the movable shaft so that it penetrates a receptacle provided in the door on the opposite side.