A disk control apparatus according to the present invention comprising a disk controller for controlling a circuit which controls read operation for reading data from a disk and a CPU for controlling the circuit and the disk controller. The disk controller comprises a buffer memory for storing data being for transferred between a host and the disk controller and a notification section for notifying the CPU that a first state in which an all buffer region of the buffer memory is stored with data to be transferred to the host transits to a second state in which a predetermined space occurs in the buffer region of the buffer memory as a result of transferring data to the host. The CPU comprises a main control section for stopping power supply to the circuit during the first state and for supplying power to the circuit in response to a notification from the notification section.