The high-speed barrier synchronization is completed among multiprocessors by saving overhead for parallel process without addition of a particular hardware mechanism. That is, the barrier synchronization process is performed by allocating the synchronization flag area, on the shared memory, indicating the synchronization point where the execution of each processor for completing the barrier synchronization is completed, updating the synchronization flag area with the software in accordance with the executing condition, and comparing, with each processor, the synchronization flag area of the other processors which takes part in the barrier synchronization.