In order to develop the new engineering materials such as mechanical sliding parts (tribomaterials) based on all inedible plants-derived materials, the purpose of this study is to investigate the gear strength of hemp fiber (HF) reinforced plants-derived polyamide 1010 (PA1010) biomass composites. PA1010 was made from sebacic acid and decamethylenediamine, which are obtained from plant-derived castor oil. HF, which is one of the natural fibers, were surface-treated by two types of surface treatment: a) alkali treatment by NaOH solution and b) surface treatment by ureidosilane coupling agent. HF/PA1010 biomass composites were extruded by a twin extruder and injection-molded. The test small spur gears (pitch diameter d0=11mm, module=0.5mm, number of teeth Z=22, tip diameter da=12mm and face width b=1.5mm) were machined from the injection-molded plate and finished by a hobbing machine. Three types of properties of spur gear machined from these HF/PA1010 biomass composites were evaluated: dedeum bending strength of the spur gear by universal tester,　gear fatigue strength by using power absorbing typed gear testing apparatus and wear amount of spur gear by same apparatus. It was found that the dedendum bending strength and the wear amount of the spur gear of PA1010 improved with the filling HF although those of HF/PA1010 biomass composites decreased with increasing the volume fraction of fiber. On the other hand, the gear fatigue strength had a maximum peak at 20vol.%. These tendencies may be due to the fundamental mechanical and tribological properties of HF/PA1010 biomass composites.