PURPOSE: To stop a sliding door surely in the midst of the side of an opening position even if a rail face is inclined to the side of a closing position by a mounting error, etc., more than is necessary by forming rear inclination face sections making a pair on which wheels are simultaneously mounted in the midest of a movable range of the wheel on the side of the closing position and in the midst of a movable range of the wheel on the side of the opening position.

CONSTITUTION: Two sets of rear inclination face sections making a pair on which wheels 31 and 32 are simultaneously mounted in the midst of a movable range A of the wheel 31 on the side of a closing position and in the midst of a movable range B of the wheel 32 on the side of an opening position are formed on a rail face 21. The rear inclination face sections 21c and 21d are respectively provided to positions lower than the reference line 22. Even if the rear inclination face sections 21c and 21d are respectively inclined in rear so that they are not inclined down to the side of the closing position even if the rail face 21 is inclined to the side of the closing position by a mounting error, etc., more than is necessary.