At the inside wall face of the first tube portion 8a of the lens barrel, the shielding grooves 20 having a saw blade shape are formed along the optical axis O, and each shielding groove 20 at least comprises the first inclined face 22 facing the image side, and the second inclined face 24 facing the object side, further the groove widths of the shielding groove 20 is constituted so that they changes in steps or continuously as getting closer to the second lens group 10b from the object side.