A stopper structure of a window pane includes a pane holder attached to a lower portion of the window pane a guide rail along which the pane holder is movable, and a stopper block attached to the guide rail. The stopper block is configured to interfere with the pane holder to limit a range of motion of the pane holder along the guide rail. The stopper block may include a main part and a protrusion, protruding from the main part. The protrusion may be riveted into a hole in the guide rail, and the main part may interfere with the pane holder.