To provide an erasable type image display medium which performs writing/erasure of an image by light and excels in image retention and an image forming method.

The image display medium 1 obtained by forming a photosensitive layer comprising a fulgide compound and an electron-accepting compound having a Lewis acid moiety and a long chain alkyl structure moiety on a support substrate is subjected to a step of allowing the fulgide compound in the photosensitive layer to develop a color by irradiation with ultraviolet light from a mercury lamp 30, a step of selectively decoloring the fulgide compound which has developed the color by irradiation with visible light in a wavelength region corresponding to the maximum absorption wavelength of the fulgide compound from light-emitting diode arrays 41, 42, 43, and a step of heating the selectively decolored fulgide compound to the melting point of the electron-accepting compound or above.

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