PURPOSE: To close the gap between a door and a floor surface with a gap closing member by a method wherein the gap closing member can be retreated to the inside of the door while the door is opened and can be projected downward when the door is shut.

CONSTITUTION: A slide bar 3 is attached to a base member 4 so that it can move horizontally approximately in parallel with the face of the under bed of a door 1, a return spring 5 is attached to a specified position on the slide bar 3, the front end of the slide bar 3 is projected slightly outward beyond the face of the side end of the door, and a pivot part 8 for a turning bar is formed to a position slightly off the center of the long-plate-like turning bar 7. The pivot part 8 is then hinged to the base member 4, the short end part 7a of the turning bar is fixed with a pin to one end 6a of a horizontally movable bar while the other end 6b of the horizontally movable bar is fixed with a pin to the slide bar 3, the long end part 7b of the turning bar is held with a bracket member provided to a vertically sliding member 10, and a gap closing member 13 is attached to the lower part of the vertically sliding member 10.