In order to measure the forced vibration of a ship excited by an oscillation exciter simultaneously at many measuring points, the author has completed a set of (ten in number) electrical vibrographs applying the variable inductance type of gauges. Making use of these vibrographs, the author has carried out a series of ship vibration experiments on four newly built ships. In this paper the author represents the principle, the construction, and the results of calibration of the vibrograph, and the results obtained on ship vibration experiments. The results obtained on vibration experiments are as follows, (1) Making use of these vibrographs, it has become possible to measure not only natural frequencies, but also instantaneous vibration profiles of a ship. (2) It has been made clear how natural frequencies of the vertical flexural vibration of a ship moored alongside the quay are effected by wall and depth of water. (3) The effect of the irregularity of angular velocity of the oscillation exciter upon the mode of vibration of a ship has been made clear.