An optical kit includes a base including a main surface; and a holding unit provided on the main surface to hold an optical system. The holding unit includes a lens holding unit that holds a lens, a reflector holding unit that holds a corner reflector, a first aperture member holding unit that holds a first aperture member, a second aperture member holding unit that holds a second aperture member, and a third aperture member holding unit that holds a third aperture member. The reflector holding unit includes a first mechanism that holds an entirety of the corner reflector so as to be rotatable along the main surface, and a second mechanism configured to adjust an optical axis of a diffracted light in each of a reflective diffraction grating and a mirror.