The authors succeeded in producing high-speed continuous patterning on the surface of plastic fiber at a feeding speed of 20 m/min by using a system they developed employing thermal roller imprint methodology. In this method, a cylindrical mold with seamless microstructures formed on its surface was used, wherein a plastic fiber is pressed between the cylindrical mold and a backup roller and is then run for imprinting. Here, the movement of the cylindrical mold in the direction of space-change between the mold and the backup roller can be precisely controlled, and the press force during the imprinting can be measured by a load cell located beneath the backup roller. The cylindrical mold and the backup roller are heated up to 250 °C and are rotated synchronously, imparting a forward-linear motion to the plastic fiber and thereby making continuous patterning of microstructures possible. Since the press force feedback system during high-speed imprinting cannot be adequately controlled, the authors devised a scheme where the system memorizes the press positions corresponding to the rotating angles of the cylindrical mold at low feeding speed under a controlled press force. Here, the periodic variation of the center-to-center distance between the cylindrical mold and the backup roller can be measured at set intervals and, by using the memorized relationship between the rotational angle and press position, the position of the cylindrical mold is then moved. Finally, the authors imprinted 50 μm high microstructures onto the surface of the plastic optical fiber whose diameter was 250 μm. As a result, when the press position was fixed, the standard deviation of the press force was 6.86 N; however, this value dropped to 2.80 N when the improved control method was employed. The range of depth variation was 8.0 μm when the press position was fixed, and this number went down to 2.2 ;- ;m when the improved control method was employed.