PURPOSE: To simplify structure and to facilitate the adjustment of diopter by supporting an objective lens so that it can be moved in an optical axis direction and moving the objective lens in the optical axis direction, thereby adjusting the diopter.

CONSTITUTION: A finder optical system is constituted of the objective lens 2, a zoom system front group lens 4, a zoom system rear group lens 5, a 1st rectangular prism 6, a 2nd rectangular prism 8 and an ocular 10. The finder optical system is arranged in a finder shielding space formed of a basic housing 12 and an upper housing 14 made of synthetic resin such as polycarbonate. The objective lens 2 is supported by a lens mount 15 where a male screw 12 is cut, and screwed in a female screw provided in the housing 12. The ocular 10 is inserted in a pair of longitudinal grooves 40 provided on an opposite side to the lens 2, that is, the rear part of the housing 12. By supporting the lens 2 so that it can be moved in the optical axis direction and moving the lens 2 in the optical axis direction, the diopter is adjusted.