To develop new polymeric engineering materials based on all inedible plant-derived materials, we investigate the influence of screw configuration in twin screw extruder on the dynamic viscoelastic properties of hemp fiber (HF) reinforced plant-derived polyamide 1010 (PA1010) biomass composites in molten state. PA1010 was made from sebacic acid and decamethylenediamine, which are obtained from plant-derived castor oil. HF, which is one of the natural fibers, was used as a reinforcement fiber. HF was surface-treated by two types of surface treatment: (a) alkaline treatment by sodium chloride (NaClO2) solution and (b) surface treatment by ureidosilane coupling agents (A-1160). These biomass composites were extruded using a twin screw extruder, and compression-molded. Two types of screw configuration in twin screw extruder: original screw (conventional type, sc1) and new type (mixing elements added type, sc2) were used in this study. Dynamic viscoelastic properties in the molten state were evaluated by oscillatory flow testing using a parallel plate-type rotational rheometer. It was found that the storage and loss moduli of HF/PA1010 biomass composites mixed by sc2 are remarkably lower than those of sc1 in the whole range of angular frequency. Thus the modification of screw configuration has stronger influence on the dynamic viscoelastic properties of the biomass composites in molten state. These may be attributed to the change in the internal microstructure formation such as fiber shape, fiber network formation and fiber dispersion in the composites.