Normal simultaneous multi-layer coating can be accomplished without allowing the coating liquids to increase in viscosity before and during their application, and inter-layer mixing can be prevented by increasing the viscosity after the application. In a method of manufacturing an information recording material in which at least one out of a plurality of layers formed by simultaneous multi-layer application of a plurality of coating liquids over a running supporting base 14 with a slide bead coating device 16 is an information recording layer, and the multi-layer coats so formed are dried by a drying device 20, at least one of the plurality of coating liquids contains PVA and boric acid whose mutual contact or mixing causes the coating liquids to increase in viscosity.