The invention belongs to the technical field of garment processing equipment, and particularly relates to a cut part trimmer. A workbench used for placing cut parts is arranged on a rack, and a gantryframe is arranged at the position, on the rear side of the workbench, of the rack; a first material pressing device used for pressing the cut parts, a cutting knife used for cutting the cut parts anda second pressing device used for pressing the cut parts are sequentially arranged on a cross beam of the portal frame from front to back; the cutting knife is driven by a first driving mechanism tomove left and right along the cross beam to conduct cutting. The cut part trimmer is high in automation degree, cutting and collection of the cut parts can be automatically carried out after feeding,the trimming efficiency is high, and the labor intensity of workers is reduced.