An image processing apparatus for processing image data comprises a printer for printing processed image data on recording paper; an image data receiver for receiving image data transmitted thereto via a network; storage unit for storing the image data received by the image receiver; a print controller for controlling printing of the image data stored in the storage unit on the recording paper; and one or more feed trays that load recording paper loaded therein and feed the loaded recording paper to the printer, wherein, if recording paper of the image data is larger in size than any recording paper loaded in the feed trays, the print controller reduces in size image data to fit with largest-size recording paper of the recording paper loaded in the feed trays, and prints the size-reduced image data on the largest-size paper.