A plastic barrel, which surrounds a central axis, includes an object-side portion and a tubular portion. The object-side portion includes an object-side opening and a reverse inclined structure. The reverse inclined structure surrounds the object-side opening and includes a reverse inclined surface and at least one annular concave structure. The at least one annular concave structure is disposed on an object side of the reverse inclined surface and recessed from the object-side opening along a direction away from the central axis, wherein a sectional surface of the at least one annular concave structure passing through the central axis includes a valley point and two concave ends, and the two concave ends are disposed on an object side and an image side of the valley point, respectively. The tubular portion is connected to the object-side portion and extends to the image side.