An image processing device is structured such that an appropriate judgement of an image, at which blurring or disappearance or the like will occur, is possible. When pixels, which form a line image at which there is the possibility that blurring or disappearance will occur at the time of printing by using a printing plate, are extracted, a line image warning function gives notice by displaying a warning message on a monitor of a client terminal. Thereafter, image converting and print setting are carried out such that an extracted line image is clarified. In this way, when a proof is prepared, an image, at which there is the possibility that blurring or disappearance will occur on a printed matter obtained by using a printing plate, is clarified, and appropriate proofing is possible.