Amyloid fibrils, which are linear proteins with widths of less than 10 nm and lengths of more than 1 μm, were used as an amorphous carbon template for graphene nanoribbons (GNRs) synthesized by solid-phase graphitization using liquid Ga as the catalyst. The crystal quality of the GNRs improved with increasing synthesis temperature. However, the shape of the GNRs synthesized at temperatures higher than 900 °C became broader, losing the original amyloid shape, whereas the GNRs synthesized at 900 °C seemed to maintain the original amyloid shape in the SEM observation. The conducting paths of GNRs synthesized at 900 °C were found to be slightly diffused outside the topography of the GNRs in the conductive atomic force microscopy map. In addition, some of the sapphire terrace edges of the substrate showed conductivity, which indicates that the growth mechanism of graphene on a sapphire substrate might be a step-flow growth mode.