A plastic barrel includes an object-end portion, an image-end portion, a tube portion and a plurality of wedge structures. The object-end portion includes an outer object-end surface, an object-end hole and an inner annular object-end surface. The image-end portion includes an outer image-end surface, an image-end opening and an inner annular image-end surface. The tube portion connects the object-end portion and the image-end portion, and includes a plurality of inclined surfaces. The wedge structures are disposed on at least one surface of the inner annular object-end surface, the inner annular image-end surface and the inclined surfaces, wherein the wedge structures are regularly arranged around the central axis, and each of the wedge structures includes an acute end and a tapered section. The tapered section connects the surface, which the wedge structure is disposed on, and the acute end.