An interference fringe generating optical system generates an interference fringe, and a magnifying optical system magnifies the interference fringe and projects the interference fringe on an object surface. The magnifying optical system includes an incident-side lens group on the side where a light beam forming the interference fringe is incident and an exit-side lens group on the side where the light beam is emitted and the interference fringe is projected towards the object surface. The expression f1/f2>3 holds, where f1 is the focal length of the incident-side lens group, and f2 is the focal length of the exit-side lens group. The incident-side and exit-side lens groups each have a positive refractive power. The expression xd/(f1+f2)