In a storage apparatus, an MPU acquires a value of power capable of being used to transition a HDD from a power-saving state to an access-enabled state, receives an access command via a host I/F, determines whether or not it is possible to respond to the access command using one or more HDD in the access-enabled state from among the HDD configuring a LU, and when it is determined that it is possible to respond, selects, from HDD in the power-saving state in the access command-targeted LU, one or more HDD, which are capable of transitioning to the access-enabled state using power in a range of usable power values, and which can make a response possible, as a target to be preferentially transitioned to the access-enabled state.