In this report the authors have offered the equations of motion and a method of their solution about the oscillation of a ship containing a large amount of liquid cargo which is liable to movement but restrained the free motion with the rolling ship, making use of the theory of the physical double pendulum, and compared a calculated example with the experiment (in case where the centre of gravity of the movable weight lies below the axis of rotation). The results show that : (1) Owing to the restriction of movement of the weight, the righting moments are considerably non-linealized. This non-linearity shifts the peak of the resonance curve to higher frequency than that in the case where the restiction is removed, but much reduction of the peak amplitude can not necessarily be expected. (2) The impulsive force due to the collision of the moving weight to the stopper (the dash of the ilquid cargo to the compartment wall in the actual cases of ships) acts as the quenching moment, thus reduces the amplitudes of oscillations.