PURPOSE: To form a group with plural processes and to perform the exclusive control of file use for the unit of the group by refusing the use right request of a certain file when the process belonging to a certain group requests the right of use to the file and the file is used by the other group.

CONSTITUTION: Each time the new process is generated at an information processor enabling the parallel operations of plural processes, a CPU 40 writes a process number pi and a group number qi of that process on a process managing table 21 and controls access to a certain file in each process according to this managing information. On the other hand, the CPU 40 manages which file each process currently performs the decleration of use to by using a file use decleration managing table 22. Then, the exclusive control of file use is performed for the unit of the group by the process managing table 21 and the file use decleration managing table 22.