Abstract: A pattern generator permitting to output patterns at high speed and having an operating function, which is suitable for generating test patterns for memory ICs. Although it was known heretofore to increase the operating speed by operating a plurality of pattern generators, for which patterns were generated from memories, in which patterns were previously stored, in parallel, it was not possible to operate pattern generators having an operating function in parallel. A method, by which the order of execution of operation processing instructions is assigned to each of the pattern generators and operation processing instructions are accumulated and allows patterns to be generated at high speed by means of a pattern generator having an operating function. Specifically, the operating processing instructions are grouped and rearranged such that all the pattern generators execute instructions in parallel.