To prevent warpage or wrinkles by eliminating the runout of an adhesive in a light quantity adjusting device for a camera where an ND filter is fixed on a diaphragm blade.

A diaphragm blade 10 for adjusting light quantity is injection- molded of resin material, a positioning projection 14 and a caulking projection 15 are integrally formed, and a positioning hole 21 into which the projection 14 is inserted and a caulking hole 22 into which the projection 15 is inserted are formed on the ND filter 20 for adjusting the light quantity, and they are fit respectively. Thereafter, the projection 15 is thermally deformed to fix the filter 20 by thermal caulking.