An external laser light introducing device is constructed to introduce laser light from outside of an optical apparatus into inside so that the laser light is condensed on a target by a condenser lens located inside the optical apparatus. In this case, the external laser light introducing device comprises a pupil projection optical system for projecting the entrance pupil of the condenser lens on an external pupil located outside the optical apparatus and an optical axis aligning mechanism for practically aligning the optical axis of the laser light with that of the external pupil.