A control apparatus configured to control power of a device that communicates with a host system via a communication interface which complies with a predetermined standard includes a reception unit configured to receive a signal indicating that the host system transitions to a predetermined power state and a determination unit configured to determine, according to reception of the signal indicating that the host system transitions to the predetermined power state, a power state of each of the device and a physical layer of the communication interface used by the device from a plurality of power states, based on a power state of the host system, a power state of the device, and a power state of the physical layer of the communication interface included in the device and complying with the predetermined standard.