PURPOSE: To project a practically flat image area having no aberration on a flat plane by compensating the image area curve of one optical subsystem from the other optical subsystem.

CONSTITUTION: For example, an object 6 of a photograph process mask is projected as a curved image 10 by an optical subsystem 8. Then, this curved image 10 is inputted to an optical subsystem 12 and projected on a semiconductor chip board 16, for example, as a practically planar and practically non- aberration real image 14. During this projection, the odd aberration is individually corrected by the respective optical subsystems 8 and 12 and the even aberration and the image area curve are compensated between both the subsystems 8 and 12. Besides, many openings can be provided over the wide area.