The automatic position and the attitude control for the underwater vehicle staying still or moving at dead slow speed becomes non-linear, because the acceleration or the deceleration motion must be applied using thrusters, while the linear control system can be applied to the underwater vehicle cruising at high speed. In the previous paper, the linear approxmation of this non-linear system and a linear design method were proposed. This paper describes the results of the sea tests of the experimental underwater vehicle, and the evaluations made by the test results which proved the thory and the design method proposed in the previous paper to be applicable to the control of these underwater vehicles.