The authors are developing an on-fiber device that uses a quartz fiber as a substrate material and a large-area display and a wearable health monitor by woven fibers with embedded electrical circuit. The electrical circuit will be formed by inserting some electroconductive material into the concave pattern by inkjet and electroless-plating after thermally imprinting on the surface of the quartz fiber. To imprint the quartz fiber, a mold should be able to withstand the high temperature of 1400 degrees C. Therefore, a mold for quartz imprinting on quartz fiber was fabricated with a glasslike carbon substrate polished by chemical-mechanical-polishing. Mold patterns with high accuracies were processed by applying microelectromechanical system fabrication techniques such as photolithography and reactive ion etching. Precise patterns with 5 mu m minimum linewidths were transferred on the front surface of a 200 mu m square quartz fiber by thermal nanoimprint technology. The width of the imprinted quartz fibers grew from 200 to 296 mu m by the loading force, but part of the loading force was also used up in deforming the quartz fibers. Filling rates, defined as the ratio of the height of imprinted patterns to the depth of mold patterns, were calculated and then the relationship between the filling rate and the aspect ratio of mold patterns was investigated. The molding accuracy was found to be independent of the size of the mold patterns, but it did exhibit its dependency on the aspect ratio of the mold patterns. The expected overlay accuracy, which is important for making circuitry in the future, was approximately 5 mu m judging from the imprinted patterns on the quartz fiber.