To provide a projection aligner which can prevent the occurrence of flare light even if the wavelength of exposed light is short, particularly, shorter than 200 nm, and can project a pattern on a substrate with a satisfactory contrast in a projection optical system of a reflection-refraction type.

An illumination optical system illuminating a mask R having prescribed pattern with the illumination light of a prescribed wavelength and a projection optical system PL projecting the pattern on the mask R on a substrate W are installed. The projection optical system PL has at least a first reflection face R1 and a second reflection face R2. At least either one of the first reflection face R1 and the second reflection face R2 has a positive refractive power. The first and second reflection faces R1 and R2 have aperture parts AP1 and AP2 which are installed near an optical axis AX and through which light passes. The reflectance of either one the first reflection face R1 and the second reflection face R2 for a prescribed wavelength is at most 95%.