PURPOSE: To eliminate a stay due to the waiting for filing of a logging data, by applying a simultaneous filing process to the subsequent logging data while the preceding logging data is filed.

CONSTITUTION: An effective process is carried out for plural logging data which are stored in a physical storage medium like a magnetic disk storage device, etc. In this case, if the filing request is produced to a program A and then B, the logging data A and B are stored in a buffer 7 and at the same time registered to a waiting line 9 in order of A and B. A filing control part 2 can file plural logging data in the line 9 with the start of filing control of one time. Thus the data A and B are filed consecutively. This can reduce the load factor of the logging file as well as the overhead of a CPU which is required for filing.