An image forming device comprises an image forming section that consecutively forms plural images on a plurality of recording media, a detecting section that detects, on the basis of an image formed in a storage medium, color development data indicating color development characteristics of the image, a warning control section that decides whether or not to issue warning information regarding the color development characteristics on the basis of the color development data detected by the detecting section and reference data which the color development characteristics are to reference, and a warning section that issues warning information regarding the color development characteristics in response to the decision by the warning control section.