PURPOSE: To lighten the manufacturing cost of a pattern barrier filter by using a filter for illumination having the function of the pattern barrier filter, using the filter for illumination which takes out only lights of two wavelengths of an illumination system.

CONSTITUTION: An illumination system makes an illumination light of wavelength α and an illumination light of wavelength β from the luminous fluxes emitted out of two light source 1 and 2 through a filter 3 for illumination and a filter 4 for illumination. The luminous fluxes of wavelengths α and β are put together with a dichroic mirror 5 through collimator lenses 18 and 19, and it is let fall to irradiate an X-ray mask face 8 and a wafer face 9, respectively, through a half mirror 6 and an objective 7. The images of a mask mark 14 and wafer mask 15 are formed in the same position by an color aberration objective 7 on the axis. These image are picked up with a CCD camera 13 through a pattern barrier filter 12. Thereby, the manufacturing cost of the pattern barrier filter an be lightened.