The invention relates to the technical field of processing of retainers, and discloses a rivet insertion device for a retainer. The device comprises a rivet-inserting upper mold, an oblique hole mold assembly and a rivet-inserting lower mold, wherein the upper end of the rivet-inserting upper mold is connected with a power output end of a power part, and the lower end of the rivet-inserting upper mold is provided with not less than one rivet-pressing pin; the oblique hole mold assembly is arranged under the rivet-inserting upper mold, the lower end of the oblique hole mold assembly is provided with an elastic mold, the elastic mold is provided with a through hole corresponding to a rivet insertion hole of a retainer which needs to be inserted with rivets, the through hole and the rivet-pressing pin correspond in a vertical direction, a lateral surface of the oblique hole mold assembly is also provided with not less than one oblique hole mold pipe, the oblique hole mold pipe is slantways arranged, and the lower end of the oblique hole mold pipe corresponds to the upper end of the through hole; and the rivet-inserting lower mold is arranged under the oblique hole mold assembly. The rivet insertion device for the retainer can insert a plurality of the rivets into the rivet insertion hole of the retainer at one time at a quicker speed, and has high production efficiency.