A storage system includes: a basic apparatus for transmitting an access request through a data input line for transmitting data; and an extension apparatus for receiving an access request from the basic apparatus through the data input line, the extension apparatus including a storage for storing data and a controller for controlling the access request from the basic apparatus, wherein the basic apparatus superimposes a voltage to the data input line in accordance with the access request, and wherein the extension apparatus includes an upper input voltage detector for detecting the voltage superimposed on the upper data input line and includes a power controller for controlling the power supply to the controller on the basis of the detected voltage.