A tube material is formed by continuously extruding a thermoplastic resin material in the shape of a cylinder that has a thickness of 100 μm and a circumferential length of 800 mm. After that, in a polishing process, the tube material is rubbed with a lapping tape of #2000 while being rotated in one direction at a fixed speed, so that circumferential stripes are formed on the outer circumferential surface of the tube material. Then, the circumferential stripes are thermally transferred by pressing the outer circumferential surface of the heated tube material against a mold surface that is finished in the shape of circumferential stripes by a thermal transfer process.