To provide a printer capable of preventing printing in color although a user does not intend to perform color printing or printing in monochrome although the user does not intend to perform monochrome printing.

Am image processor 102 includes a color/monochrome determiner 51 and a controller 108. When color setting is in a full color mode or a monochrome mode, the color monochrome determiner 51 determines whether color image data inputted expresses a color manuscript or a monochrome manuscript. When it is determined that the color image data expresses the monochrome manuscript when color setting is in the full color mode, or when it is determined that the color image data expresses the color manuscript when color setting is in the monochrome mode, the controller 108 displays a message indicative of the determination on an image display device 104.