To enhance mountability of the subject stopper in mounting on a hanger bracket at the upper end of a sliding door, a stopper against which a cushion provided on the building side is pressed, by providing the stopper with a pair of leg pieces located on the front and back of the bracket, and causing a screw driven into one of the leg pieces in prop form against the bracket.

A second leg piece 30 made of a metal with an inverted-L- shaped cross section is inserted into a slit 29 cut in the horizontal part 28a of a stopper main body 28, with its horizontal piece 30a stacking up on the horizontal part 28a of the stopper main body 28. Then a screw is driven into a tapped hole 31 provided in the leg piece 30, and a hanger bracket 13 is pressed between the screw and a first leg 28b provided at the stopper main body 28, so as to secure a stopper 27 to the bracket 13. Thus the stopper 27 can easily be secured to a optional position of the bracket 13, fine adjustments of the position of the stopper 27 can be made accurately, and one kind of bracket 13 can be used for plural kinds of sliding doors with different widths without being machined specially.