An image forming method is provided to attain a higher security for preventing forgery and falsification of information by using an optical diffraction structure. In a body (10) whereupon a layer is to be transferred, printing information (2) is recorded. On the body (10), a layer (20d) including a hologram and a diffraction lattice provided on an optical diffraction structure transfer sheet (20) is transferred, and an image including recorded printing information (2) and optical diffraction structures (3, 4, 5) is formed. The layer (20d) including the optical diffraction structure is transferred so that the diffraction lattice (5) to be transferred forms diffraction lattice information (5) showing a prescribed regularity in a corresponding relationship between the printing information (2).