PURPOSE: To shorten the sampling cycle and to stabilize a motion control system of an underwater sailing object, etc., without using any special hardware nor software in an attitude angle detecting system which is applied to an attitued angle detector.

CONSTITUTION: An attitude angle detecting system includes an attitude angle detector 11 which detects the attitude angle of underwater sailing objects and a controller 12 which gives the detecting commands to the detector 11. Then the detector 11 and the controller 12 are connected together by communication. In such a constitution of the system, the attitude angle calculation rate of the detector 11 is set equal to the rate of the command signals given from the controller 12. Then the attitude angle of an underwater sailing object is operated when a command signal is received from the controller 12. The result of this operation is sent back to the controller 12.