An image formation method including forming at least one invisible image selected from invisible images formed when (a) forming only an invisible image on the surface of an image output medium, (b) forming an invisible image and a visible image by laminating these images one by one on the surface of the medium and (c) forming an invisible image and a visible image separately in different regions on the surface of the medium, in which at least one of the images (a), (b) and (c) is composed of a two-dimensional pattern, and in which the invisible image is formed using a toner that includes at least a binder resin and a near-infrared light absorbing material of inorganic material particles in which the rate of absorption in the visible region of the toner is 15% or less and the average dispersion diameter of the absorbing material is 50 800 nm.