To reduce the load of an I/O node, to improve the performance of an input and output processing, and to improve the performance of a whole system in a parallel computer in which plural computer nodes are connected in a network.

One logical file 51 is divided and stored in secondary storage devices 61 and 62 on plural I/O nodes 31 and 32, and the input and output of the file is operated in parallel. A metafile 21 indicating this logical file 51 is prepared, and the logical file 51 is connected with the substance of the file stored on each I/O node 31 and 32 by the metafile 21. This metafile 21 is provided on the secondary storage device to which reference can be attained from all calculating nodes 1a-1c. At the time of generating the logical file 51, the number of division and the data length of division can be designated.