To eliminate H/W blocks which are unnecessary for software(S/W) processing for a microprocessor (μP) by determining a hardware(H/W) subelement obtained and determining a scale when the total time needed to execute decomposed microcodes is equal to or shorter than a software(S/W) process upper-limit time.

The clock period of a μP software core is given as information (step S3) and the execution processing time obtained from the number of S/W program processing steps is compared with a system request performance (step S5). When the processing tine has margin for system request performance, a microcode which performs other equivalent processes using no exclusive H/W block is substituted for (step S6). A system processing time, on the other hand, is calculated (step S14) and compared with a system processing restriction time (step S15). When the system processing restriction time is not exceeded and the processing can be performed, a multiplier is unnecessary finally and the area reduction of the μP software core is determined (step S17).