A new experimental tank for seakeeping and manoeuvring tests has been completed at Yokohama Research Institute of Ishikawajima-Harima Heavy Industries Co., Ltd. The tank is 70 m × 30 m in effective area and 3.0 m in water depth. The tank has a carriage system which consists of a main carriage, sub-carriage and turning table. The main carriage laid across the span of 32.6 m moves lengthwise and a sub-carriage pendent from the main carriage moves breadthwise. One of the features of the tank is that the sub-carriage has a turning table 3.0 m in diameter, the motion of which is controlled synchronously with those of the main and sub-carriage. The control systems of the carriage are set in the control room on the shore, and the powers and signals for controlling the carriages are supplied with special cable hanging apparatuses (cable bear). The carriage systems follow automatically a model running freely with the aid of X-Y analizer without any contacts. The newly developed hydraulic actuators are applied for the wavemakers. They are called electro-hydraulic step cylinder, and the ports of which are controlled digitally with incremental pulse signals.