To cope with oscillation in both pitching and rolling developed by a marine vessel by means of one equipment.

A turn table 12 is set over a marine vessel 1. A casing 9 provided with a bottom plate 2 in the longer direction, which is curved in such a way as to be swelled downward at its center, is mounted onto the turn table 12, and a weight is attached onto the bottom plate 2 in such a way as to be freely moved in the longer direction. Pin holes 15a and 15b are provided for places mutually dislocated by 90° with respect to the turning center of the turn table 12, and a locking hole 17 is provided for the side of the marine vessel 1. When the turn table 12 is turned around until the pin hole 15a coincides with the lock hole 17 so as to allow a lock pin 16 to be inserted therein, the casing 9 can be aligned with the direction of rolling, and when the turn table 12 is turned around until the pin hole 15b coincides with the lock hole 17 so as to allow the lock pin 16 to be inserted therein, the casing 9 can thereby be aligned with the direction of pitching.