The present invention enables to ensure printing the entire desired image. An image data interpreter 21 interprets the header portion of data transmitted by a digital camera to detect the number of dots indicative of height and width of an image to be printed. A printer analyzer 22 detects the size of a print paper actually set in a printer. To perform printing in a print condition set by an output setting unit 23, image data size is adjusted based on the detected image data size and print paper size as well as the set print condition, and the adjusted image data is outputted to a printer engine.