An investigation was carried out to elucidate the nature of the natural vibrations on the outer ring itself of the tapered roller bearing. In this paper, the vibrations of seven outer rings of the tapered roller bearing were studied. In the experiments, the outer ring itself was struck in the radial or the axial direction. The sound generated by the strike was measured by a condenser microphone. Natural frequencies of the outer ring itself were determined from the frequency spectra of the sound. Moreover, a theoretical approach was taken toward the measured natural frequencies. From the experiments, analysis and considerations, the natural vibrations on the outer ring itself of the tapered roller bearing were clarified, and it was found that the frequencies of the natural vibrations could be calculated by extending the theory of Kirkhope et al.