A drive system determines a combination of basic patterns (type of basic patterns to be generated and the number of pulses of each basic pattern) based on design data of patterns and pattern combination information stored in a memory. Then, based on the determined result, each micro mirror of a variable molding mask is individually controlled such that a plurality of basic patterns are sequentially generated according to each of the number of pulses, and each basic pattern generated by the variable molding mask is sequentially image-formed on a plate via a projection optical system. Thus, a pattern with a desired line width corresponding to the design data is formed at a desired position on the object with a good accuracy.