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 α(p, n) for a portion to be sequentially processed, processing time β(p, n)/p for a portion to be parallel processed and processing time σ(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 Rpara(p, n), a sequential calculation time ratio Rα(p, n) and a parallel overhead ratio Rσ(p, n) are calculated by using the obtained processing time σ(p, n) for the portion to be sequentially processed, β(p, n) for the portion to be parallel processed and σ(p, n) caused by the overhead for the parallel processing. A parallel efficiency Epara(p, n) is calculated in accordance with an expression 1/Rpara(p, n)×(1−Rα(p, n)−Rσ(p, n)).