The present invention is to clarify causes of hampering the performance by quantitatively associating a value of a parallel efficiency with factors of hampering the improvement of the performance of a parallel computer system, Processing time (p, n) for a portion to be sequentially processed, processing time (p, n)/p for a portion to be parallel processed and processing time (p, n) caused by an overhead for the parallel processing at the time of the execution of a parallel processing program are measured. A parallelized rate R_para(p, n), a sequential calculation time ratio R(p, n) and a parallel overhead ratio R(p, n) are calculated by using the obtained processing time (p, n) for the portion to be sequentially processed, (p, n) for the portion to be parallel processed and (p, n) caused by the overhead for the parallel processing. A parallel efficiency E_para(p, n) is calculated in accordance with an expression 1/R_para(p, n)(1-R(p, n)-R(p, n)).