In the case of a flap driven small aircraft, to implement forward and reverse flap drive movements and generate the energy required during flight, the unidirectional rotational electric motor is operated in both directions using the drive mechanism of the wing drive device composed of numerous gears and links. Therefore, to ensure the flight performance and reliability of the aircraft, accurate repeatability and reproducibility must be guaranteed above a certain level when the wing drive device operates. In this study, to improve the performance of a small flapping aircraft, weight reduction and quality improvement of the driving device are achieved by changing the module of the internal gear in the gearbox, which is the core of the wing, and surface treatment. In terms of the surface roughness, gear characteristics, surface treatment, and motor characteristics, we aimed to verify the performance improvement effect.