The storage control device of the present invention uses a plurality of queues to manage cache segments which are in use, so as to retain cache segments which contain large amounts of data for long periods of time. One of the queues manages segments in which large amounts of valid data are stored. Another queue manages segments in which small amounts of valid data are stored. If the number of unused segments becomes insufficient, then a segment which is positioned at the LRU end of the other queue is released, and is shifted to a free queue. Due to the use of this other queue, it is possible to retain segments in which comparatively large amounts of data are stored for comparatively long periods of time.