Use situations of storage devices utilizing a storage area network (SAN) are predicted and the devices are automatically managed on the basis of the predicted results. To manage the devices utilizing the SAN, there is established the policy prescribing actions each executed when some object to be judged satisfies some condition with regard to storage devices. Information concerning use situations of the devices is collected and a value of an object to be judged of the policy is calculated based on collected information to judge whether the value of the object to be judged satisfies a condition of the policy. When the condition is satisfied, the action of the policy is executed. The objects to be judged of the policy may be actual result values in the past, current values or prediction values in the future relative to use capacity of storages, the number of I/O operations of disk or fragmentation.