PURPOSE: To project and expose a pattern formed on the first object onto the second object accurately by a device wherein a light-shading device having an opening corresponding to the pattern can be moved in the direction of an optical axis along the light path in linkage with the thickness of the first object.

CONSTITUTION: A light flux radiated by a light source 11 uniformly illuminates a surface A of a light-shading device 18 after reflection and refraction through various optical elements 12W17 in succession. The light flux illuminating the exterior part of an opening 35 at the light-shading device 18 is shaded with four light-shading plates 34, while the light flux passing through the opening 35 illuminates a patterned surface B on a reticle 22. The reticle 22 is replaced with another reticle made of glass, etc. whose thickness at the transparent part differs from that of the reticle 22 so that a compatible relation can be maintained even when the refractive index changes. The size and position of the opening 35 can be adjusted in such a manner that the opening 35 is rotated and moved with the four motors 31 driven by a signal whose magnitude corresponds to the size of the reticle 22 and which is output from a projection printer incorporating said illuminating device (for example, from an electronic processing device for the stepper). Accordingly, it is made possible to illuminate an area in agreement with the surface area 22a for circuit patterns on the reticle 22.