In a storage system having a first storage control apparatus and a second storage control apparatus, the first storage control apparatus has: a first memory; a second memory; an input/output control unit for data transfer information in the second memory; and a data transfer control unit having a data buffer and a data transfer register for controlling data transfer between the first memory and second storage control apparatus based on the data transfer information read from the second memory and written in the data transfer register. When a second data transfer is controlled while a first data transfer is controlled, the data transfer control unit writes the first data transfer information and data stored in the data buffer into the second memory, reads the second data transfer information from the second memory and writes the second data transfer information into the data transfer register to control the second data transfer.