PURPOSE: To allocate file data on a disk and to follow a fast access.

CONSTITUTION: On the respective disks of a desk drive 3, a data control part to show the presence of the use of a disk page and a control table to show the existing position of a file are positioned at the center. In a device main body 2, a buffer 5 to pass the file data on a disk is held. When the allocating processing is performed, the presence of data and the file to which the data belong are investigated for each disk page for respective files, and at the time of the different file, the data are passed to the buffer 5, and when there are the passing data at the same file, they are rewritten to the data. When the file is the same one, the data are moved, and the allocation of the file on the disk is performed.