Photomask material

A photomask material which comprises an transparent support which is a plate or film of glass, natural or synthetic mineral, or synthetic resin, having thereon a transparent electroconductive layer comprised of gold, platinum, palladium, tin (IV) oxide or indium (III) oxide and having a thickness ranging from about 0.005 to 0.06.mu. and a surface electric resistivity of about 10.sup.6 ohm square or less, said electroconductive layer having thereon a transparent porous aluminum oxide layer formed by anodic oxidation, said aluminum oxide layer having a thickness of from about 1.5 to 30.mu. and containing over the entire layer a uniform distribution of fine pores ranging in size from 200 to 1000 A with a light-sensitive silver halide incorporated therein.