A plastic barrel including an object-end portion, a holder portion, and a tube portion is proposed. The object-end portion includes an outer object-end surface, an object-end hole, and an inner annular object-end surface. A part of the inner annular object-end surface is connected with the outer object-end surface and surrounding the object-end hole. The holder portion includes a bottom surface, a bottom hole, and an outer bottom side. The bottom surface surrounds the bottom hole and is connected with the outer bottom side. The holder portion further includes cut traces formed by partially removing gate portions. The tube portion includes inner annular surfaces and connects the object-end portion with the holder portion.