A method for producing a resin substrate coated with a titanic acid film, characterized in that it comprises providing a suspension of a scaly titanic acid by treating a layered titanate with an acid or warm water and allowing a basic compound having a force swelling the interstice of the layer to act thereon, to swell or separate the layer, applying the suspension on a resin substrate, and subjecting the resultant substrate to a heat treatment at a temperature less than the softening temperature of said resin substrate, preferably at a temperature less than 100° C., to thereby form a titanic acid film on the resin substrate. The above method can be suitably used for forming an inorganic coating film excellent in transparency, surface hardness, gas-barrier property and the like on any type of resin substrate with good adhesion property.