To provide a variable cycle type anti-rolling water tank device for controlling a variable cycle type anti-rolling water tank in accordance with efficiently and precisely measured data for a rolling angle.

An AD conversion board 13a and a RS232C port 13b are provided as interfaces to a central control device 10. The measured data for the rolling angle is downloaded from a rolling angle detector 38 provided outside the variable cycle type anti-rolling water tank device for measuring the attitude of a hull during navigation, through the AD conversion board 13a or the RS232C port into the central control device 10, where statistic processing means 10a processes the measured data for the rolling angle.