PURPOSE: To eliminate the decrease of the number of point light sources in a tertiary light source when a coherence coefficient is changed and to form a resist pattern having high erectness and high accuracy by forming an enlarged image or a reduced image of a secondary light source and using the image of this secondary light source as a tertiary light source.

CONSTITUTION: An illuminating optical system is constituted of a fly's eye lens 200, a lens 210, a diaphragm 220 and a condenser lens 30. In such a state, an image which has enlarged or reduced a secondary light source 250 formed by an optical element such as the fly's eye lens 200, etc. through the lens 210 is formed between the optical element and the condenser lens 230, the image of this secondary light source 250 is used as a tertiary light source 260, and a coherence coefficient is adjusted by the size of the tertiary light source 260. In such a way, the coherence coefficient can be adjusted without decreasing the number of spot light sources, and a resist pattern having high erectness and high accuracy can be formed.