A disk array apparatus using an SAS can transfer data without lowering a transfer efficiency of data even if rates of a plurality of physical links connected to a controller and storage device are different. A plurality of HDDs are connected to a controller through an expander. Data are transferred from the controller to the expander and then to HDD. In this connection, the controller and the expander transfers a set of transfer data in a plurality of the HDD-side physical links. The controller-side physical link integrates the transfer data, and multiplexes them to transfer. A plurality of HDDs-side physical links separates the transfer data to transfer in parallel.