An image processing apparatus comprises image processing units adapted to process image data obtained from an image input unit, a first memory that stores image data that has been processed by the image processing units, a first bus that transfers the image data between the image processing units and the first memory, a second memory that stores image data transferred from the first memory, a second bus connected to the first memory and the second memory; and a control unit adapted to control the transfer of the image data stored in the first memory to the second memory via the second bus based on a signal from the image processing units indicating that image processing is not currently performed.