To provide a stopper for a folding door, which can hold an elasticity holding force of a fitting groove over a long period of time, and facilitates change of its elasticity by connecting a detachable spring member to a single type of stopper plate.

The stopper for the folding door consists of a synthetic resin stopper plate 2 which is almost quadrangular as viewed in a plan view, and an almost U-shaped metallic spring member 11. The stopper plate 2 has the fitting groove 1 formed therein, which opens toward one edge of the plate to receive a traveling shaft portion 9 of a sliding body 8 of a door 10, and an attaching portion A to be attached to a rail B at the other edge thereof. The spring member 11 is detachably fitted on the stopper plate 2 along three side surfaces of the same except for the one edge toward which the fitting groove 1 opens.