An optical apparatus comprising: a reflecting member including a first reflecting surface and a second reflecting surface ; an optical system including a plurality of reflecting surfaces (3, 4, 5, 6, 14-1, 14-2, 14-3, 14-4) and configured to output light from the optical apparatus via a first light path, by sequentially reflecting light, which has been reflected by the first reflecting surface , on the plurality of reflecting surfaces (3, 4, 5, 6, 14-1, 14-2, 14-3, 14-4) to guide the reflected light to the second reflecting surface and outputting the light reflected by the second reflecting surface ; a driving part configured to change an angle of incidence of the light on the first reflecting surface of the reflecting member ; and a control means configured to control the driving part so that the first light path by which the light reflected on the second reflecting surface is output from the optical apparatus can be controlled, characterized in that , the apparatus further comprises: a light incident portion , not included in the first light path, configured to indicate a position of incident light for adjusting a position and an angle of light entering the optical system, and wherein the optical system is further configured to guide the light which has been reflected by the first reflecting surface and has not been reflected by the second reflecting surface , to the light incident portion via a second light path not including the plurality of reflecting surfaces (3, 4, 5, 6, 14-1, 14-2, 14-3, 14-4) of the optical system , and wherein the control means is configured to control the driving part to change a path of the light which has been reflected by the first reflecting surface , between the first light path and the second light path. a reflecting member including a first reflecting surface and a second reflecting surface ; an optical system including a plurality of reflecting surfaces (3, 4, 5, 6, 14-1, 14-2, 14-3, 14-4) and configured to output light from the optical apparatus via a first light path, by sequentially reflecting light, which has been reflected by the first reflecting surface , on the plurality of reflecting surfaces (3, 4, 5, 6, 14-1, 14-2, 14-3, 14-4) to guide the reflected light to the second reflecting surface and outputting the light reflected by the second reflecting surface ; a driving part configured to change an angle of incidence of the light on the first reflecting surface of the reflecting member ; and a control means configured to control the driving part so that the first light path by which the light reflected on the second reflecting surface is output from the optical apparatus can be controlled, characterized in that , a light incident portion , not included in the first light path, configured to indicate a position of incident light for adjusting a position and an angle of light entering the optical system, and wherein the optical system is further configured to guide the light which has been reflected by the first reflecting surface and has not been reflected by the second reflecting surface , to the light incident portion via a second light path not including the plurality of reflecting surfaces (3, 4, 5, 6, 14-1, 14-2, 14-3, 14-4) of the optical system , and wherein the control means is configured to control the driving part to change a path of the light which has been reflected by the first reflecting surface , between the first light path and the second light path. <EOS>