To provide a control method for a course of an underwater navigating body which saves on the energy of the power of a horizontal thruster and a vertical thruster for controlling the posture of the underwater navigating body.

The underwater navigating body 1 has a horizontal thruster 7 arranged along the horizontal axis extending in the right-to-left direction of a hull body, and navigates on the predetermined route. When the difference is generated between the course and the azimuth of the hull body under the influence of the tidal flow, and the angle formed between the course and the direction of the hull body is equal to or less than the predetermined angle, the horizontal thruster is not operated.