A RAID group control device for performing access control over one or more RAID groups each having redundancy. The RAID group control device includes an acquiring unit to acquire access frequency information with respect to a RAID group among the one or more RAID groups; a scheduling unit to find a time period exhibiting a lower access frequency than access frequencies of anterior and posterior time periods in a specified time range on the basis of the access frequency information, and to determine start timing of a process of rewriting firmware of drives belonging to the RAID group on the basis of the found time period; and a firmware rewrite processing unit to start the process of rewriting the firmware of the drives at the determined start timing.