A lens including a lens portion having first and second opposite oblong surfaces is disclosed. At least one of the first and second oblong surfaces of the lens portion is a curved lens surface having a reflective power. A rib portion is disposed at each of two opposite sides of the lens portion facing in a direction of a width of the first oblong surface. The rib portion extends along a longitudinal direction of the lens portion in a position separate from the second oblong surface. A draft surface extends between the second oblong surface and the rib portion. The draft surface includes a slant surface slanting outwardly toward the rib portion. The slant surface is curved inwardly with a draft thereof increasing gradually toward the rib portion.