Natural frequencies of flexural vibration of gear body were measured and compared with the calculated results by Mindlin's method. The relations between these natural frequencies and spectra of circumferential, radial and axial vibrations were investigated. The circumferential, radial and axial vibration accelerations and the root stresses were measured under different running conditions by using a gear testing machine of a power absorbing type. On the basis of these results the effects of web arrangements on vibration and dynamic load were clarified to a considerable extent.