PURPOSE: To satisfactorily correct aberration by successively arranging a condenser lens group having positive refracting power, 1st mirror which deflects an incident luminous flux at a right angle, master lens group which has positive refracting power and 2nd mirror which deflects the incident luminous flux at a right angle so as to satisfy specific conditions.

CONSTITUTION: The condenser lens group C having the positive refracting power, the 1st mirror R1 which deflects the incident luminous flux at a right angle, the front group Mf consisting of two pieces of positive lenses and a piece of negative lens, the master lens group M having the positive refracting power, master lens group M having the positive refracting power and the 2nd mirror R2 which deflects the incident light luminous flux further at a right angle are arranged successively from the imaging plane side of the photographing lens OL to the reimage plane side of a relay lens system RL so as to satisfy the specific conditions, i.e., 0.25<β<0.75, β<0, 0.04<d0/fc<0.13. Here, β is the magnification of the relay lens system RL, d0 is the axial distance from the imaging plane of the lens OL up to the condenser lens group C, fc is the focal length of the lens group C. The aberration is thereby satisfactorily corrected.