A storage apparatus includes a storage unit for storing data read/written by a host computer and provides the host computer with a storage area of the storage unit as one or more volumes. The storage management computer includes a first memory for storing task information including contents of an operation process performed on the storage apparatus, as well as a scheduled starting time and scheduled termination time of a process. In the case where first task information is stored in the first memory, when resources used in the process of second task information stored in the first memory are the same as resources used in the process of the first task information, the storage management computer computes times required for executing the first task information and the second task information, based on a time during which the processes of the first and second task information conflict with each other.