A light pass aperture module, in order along a central axis, includes a blade assembly and a cap. The blade assembly includes a plurality of blades. The blades form a light pass aperture, and the light pass aperture is variable in size with the central axis as a center. The cap covers the blade assembly. The cap has a through hole, and the through hole is disposed corresponding to the light pass aperture. The cap includes a surface level down structure. The surface level down structure is disposed corresponding to one of the blades, and the surface level down structure is closer to the one blade than the through hole.