An objective is to allow a storage apparatus to accurately locate a failure site upon occurrence of a failure. Provided is a storage apparatus 10 including: a controller 11 that performs data input and data output into and from a storage drive 171 in response to a data input/output request sent from an external device 2; and expanders 112, 121 each having a switch circuit 1122 provided with a physical port (Phy 1121). In this storage apparatus 10, the controller 11 performs a loopback diagnosis on the expanders 112, 121, and performs a connection-based diagnosis on a target device by sending a connection frame thereto, the target device being a device detected as having a failure. When a response to the connection frame includes information indicating a failure, the controller 11 disables the physical port to which the target device is coupled, or the physical port of the switch circuit 1121 existing on a path from the controller 11 to the target device.