A method for forming a thermal transfer printing sheet, including (a) feeding a release sheet having a release surface; (b) transferring an image, which is to be thermally transferred and printed on a transfer medium, onto the release surface of the release sheet; (c) forming a thermoplastic resin pattern, which corresponds to the image as a transfer base material and which is to be colorless and transparent by heat and pressure, and transferring the thermoplastic resin pattern onto the release surface of the release sheet; and (d) fixing the image and the thermoplastic resin pattern onto the release surface of the release sheet in a film shape, through heat and pressure.