In order to investigate the durability of the sliding parts of machinery, it is important to know the force acting on such parts and to evaluate their stress distribution. However, the actual contact stress distribution differs from the theoretical one, as in the case of the gear tooth flank. This is caused by inaccurate assembly and deformation or slant of the shaft and the bearing housing that supports the gear unit. Therefore, it is important to know the contact stress distribution on tooth flanks in the actual gear unit. The authors applied thin-film pressure sensor technology developed to measure the oil-film pressure distribution of engine sliding parts. In the present study, a thin-film pressure sensor with a thickness of approximately 6μm and 5 point sensing parts was developed and deposited along the tooth flank on the pitch circle to measure the axial pressure distribution between meshing tooth flanks. Afterward, the measured and calculated results were compared. The measured pressures were much higher than the Hertzian pressures, and were distributed unevenly along the tooth trace. Thus, it seems to have been caused by crossed and parallel misalignments and also by the shape of the tooth flanks.