An object of the present invention is to perform accurate and appropriate steering control. An automatic steering system for automatically traveling a work vehicle along a set turning circle, including a reference point calculation unit for calculating the position of a reference point VP in the working vehicle, a center P of the turning circle, and a reference point. A reference straight line calculation unit that calculates a straight line passing through VP as a reference straight line BL, a vehicle body azimuth calculation unit that calculates a vehicle body azimuth indicating the direction of the vehicle body of the work vehicle, and a line that passes through the reference point VP and is perpendicular to the reference straight line BL. An azimuth deviation amount calculation unit that calculates the intersection angle with the vehicle body azimuth as the azimuth deviation amount θ, a deviation direction determination unit that determines the positional relationship between the reference point VP and the outer circumference of the turning circle, and a reference point VP that is the outer circumference of the turning circle. And a steering control unit that outputs a steering amount that reduces the heading deviation amount θ when located inward. [Selection diagram] Fig. 13【課題】正確で適切な操舵制御を行うことを目的とする。【解決手段】設定された旋回円に沿って作業車を自動走行させる自動操舵システムであって、作業車における基準点ＶＰの位置を算出する基準点算出部と、旋回円の中心Ｐと基準点ＶＰとを通る直線を基準直線ＢＬとして算出する基準直線算出部と、作業車の車体の向きを示す車体方位を算出する車体方位算出部と、基準点ＶＰを通り基準直線ＢＬに垂直な線と車体方位との交差角を方位ずれ量θとして算出する方位ずれ量算出部と、基準点ＶＰと旋回円の外周との位置関係を判定するずれ方向判定部と、基準点ＶＰが旋回円の外周より内側に位置する場合、方位ずれ量θが小さくなる操舵量を出力する操舵制御部とを備える。【選択図】図１３
