A storage system coupled to host computers, includes: a plurality of disk drives; a plurality of processors, each controlling data reception and data transmission between the host computers and the disk drives; a shared memory for storing control information; and a plurality of shared memory control units provided for a plurality of the processors, respectively for controlling access to the shared memory from the processors. The processor transmits a plurality of first requests to the shared memory control unit that is provided for the processor and transmits a second request. Each first request initiates the access to the shared memory. The shared memory control unit receiving the first requests accesses the shared memory a plurality of times substantially at the same time and returns an access result derived by the access to the shared memory to the processor in response to the second requests.