Abstract: A photochromic material comprising a thin film of montmorillonite intercalation compound which has as a guest organic metal complex ions exhibiting a property of accepting electrons in a photo-excited state,a photochromic device comprising; (i) a transparent electrode layer 1, (ii) a transparent layer 2 of polycrystalline n-type semiconductor, (iii) the above-mentioned thin film 3 of montmorillonite intercalation compound, (iv) an electrolytic layer 6 containing an electron-donative reducing agent and (v) an opposed transparent electrode layer 4, anda method for recording and erasing information, comprising the steps of forming the above-mentioned thin film 3 of montmorillonite intercalation compound over the transparent layer 2 of polycrystalline n-type semiconductor, irradiating with light the thin film 3 in contact with the electrolyte 6 containing an electron-donative reducing agent to develop color on the irradiated site of the film and applying a bias voltage to the film being exposed to light to remove