The vessel azimuth control apparatus has an azimuth control unit that outputs a steering-angle command signal for making a vessel turn to an azimuth to which the vessel should travel, based on an azimuth command signal generated by an azimuth command generation unit, a yaw-angle signal, and a yaw-angular-velocity signal, a steering-angle control unit that controls a rudder based on the steering-angle command signal, and a control gain adjustment unit that has a calculation feasibility determination unit for determining feasibility of calculation of frequency responses, based on the yaw-angle signal and the yaw-angular-velocity signal, and that calculates respective frequency responses of the yaw-angle signal and the yaw-angular-velocity signal for the steering-angle signal, when the calculation feasibility determination unit determines that calculation of frequency response are feasible, and then adjusts a control gain of the azimuth control unit.

An attitude detection device includes a rudder angle sensor, a speed sensor, an inertia sensor, and a control device. The rudder angle sensor detects a rudder angle of a ship. The speed sensor detects a speed of the ship. The inertia sensor detects information related to an inertial force applied to the ship. The control device finds a centrifugal force applied to the ship on the basis of a signal output from each of the rudder angle sensor and the speed sensor. The control device acquires an inclination of the ship on the basis of the signal output from the inertia sensor. The control device corrects the inclination of the ship on the basis of the output of the inertia sensor according to the centrifugal force applied to the ship.

An attitude detection device includes a rudder angle sensor, a speed sensor, an inertia sensor, and a control device. The rudder angle sensor detects a rudder angle of a ship. The speed sensor detects a speed of the ship. The inertia sensor detects information related to an inertial force applied to the ship. The control device finds a centrifugal force applied to the ship on the basis of a signal output from each of the rudder angle sensor and the speed sensor. The control device acquires an inclination of the ship on the basis of the signal output from the inertia sensor. The control device corrects the inclination of the ship on the basis of the output of the inertia sensor according to the centrifugal force applied to the ship.