A plastic barrel includes an object-end portion, an image-end portion, an inner tube portion and a plurality of protrusions. The object-end portion includes an outer object-end surface, an object-end hole and an inner annular object-end surface. One side of the inner annular object-end surface is connected to the outer object-end surface and surrounds the object-end hole. The image-end portion includes an outer image-end surface, an image-end opening and an inner annular image-end surface. The inner annular image-end surface is connected to the outer image-end surface and surrounds the image-end opening. The inner tube portion connects the object-end portion and the image-end portion and includes a plurality of inclined surfaces. The protrusions are disposed at least on one of the inner annular object-end surface, the inner annular image-end surface and the inclined surfaces, wherein the protrusions are regularly arranged around the central axis of the plastic barrel.