To reduce the running cost of an ink ribbon, and to obtain printed matter having improved image quality and durability.

By taking the combination of a plurality of ink-coated areas coated with a plurality of color inks for forming an image on a recording paper by thermal sublimation and n-surfaces (n is integer 2) of image protecting layer areas separately coated with an image protecting layer for protecting the image so as to be thermally transferred on the surface of the image formed on the recording paper as one unit, the ink ribbon is constituted by successively forming a plurality of the combination units on the surface thereof. In the image forming method using such the ink ribbon, each ink-coated area and each image protective layer area of the ink ribbon are heated by a thermal head, then, the image is formed on the recording paper, and also, the image protecting layer is thermally transferred while covering at least the image-formed part. The plurality of ink-coated areas per unit of the ink ribbon are repeatedly used, and images as many as n-times are formed on the recording paper, and whenever the one-time operation of forming the images is finished, at least one of the plurality of image protecting layers is selected, and the selected image protecting layer is thermally transferred.