An analysis is made of the dynamic magnification factors in the higher modes of ship vibrations, using the experimental data obtained from full-scale vibration tests. From these data, it is derived that the values of dynamic magnifiers have the general tendencies to decrease evidently at the natural frequencies over 300 c. p. m. in the case of vertical vibration and over 350 c. p. m. in the case of horizontal vibration. In order to investigate these phenomena, the author has carried out some theoretical calculation, and it becomes clear that the local vibrations of ship have a great influence upon the magnitudes of dynamic magnifiers. And using these actual ships' data, the author derives some empirical formula for estimating the magnification factors in the higher modes of ship vibrations.