Provided is a restricting blade 21 which includes a blade substrate 21w and a blade end face 21u defining an aperture diameter as being an end face of the blade substrate 21w, while the blade end face 21u includes a first slant portion 21p which is curved and slanted against an optical axis O, a first leading end portion 21q which forms a leading end of the first slant portion 21p, a second slant portion 21r which is curved and slanted in the approximately same direction as the first slant portion 21p as being overlapped with the first slant portion 21p along the optical axis O, and a second leading end portion 21s which forms a leading end of the second slant portion 21r and the first leading end portion 21q is further protruded toward the optical axis O than the second leading end portion 21s.