An investigation is made of the virtual inertia coefficients of the vertical vibration of ships by means of the strip method with taking the effects of virtual rotatory inertia of the water and the threedimensional motion into account. In the present investigation, the consideration is made in conformity to the results of the vibration mesurements on a wooden model of tanker. For estimating the three-dimensional correction factors of the virtual inertia coefficients of the vertical vibration of ships, the experimental studies on the vibration of the cylindrical solid models having several kinds of the sectional forms are carried out and its results are taken into account. The analyses on the three-dimensional motion of the circular and elliptic cylinders on water, and the experimental studies on the measurements of the virtual inertia coefficients of the vibrations of the solid beams and a tanker model are presented in Appendices I and II respectively in the present paper.