A study is made of the three-dimensional virtual mass moment of inertia on the torsional vibration of an elliptical cylinder of finite length vibrating on the water with half-immersed draught. By taking the ratio of the three-dimensional virtual mass moment of inertia to the two-dimensional one on the torsional vibration of the elliptical cylinder, the correction factors are obtained in zero-node to three-node modes of the torsional vibrations of the elliptical cylinder. The computed results are applied to the correction factors for the torsional vibrations of a ship including higher modes, taking into account the beam-draught ratio and the length-draught ratio as parameters.