In this study, the estimation accuracy of the elastic modulus of timbers by a tapping-tone method used as a nondestructive test was examined against the real elastic modulus by the destructive test, changing section size, specimen length and kind of the timbers named Douglas fir, Chamaecyparis obtusa and Cryptomeria japonica. The elastic modulus were measured by two different types of tapping-tone method: the longitudinal vibration method and the transverse vibration method. The conclusions are as follows: it is found that the transverse vibration method predicts remarkably well the elastic modulus by the destructive test, regardless of the section size and the length of the specimen. On the other hand, the longitudinal vibration method to the small-size specimen (specimen with 480 mm length) shows, in certain cases, wrong estimation against the elastic modulus of the destructive test.