To provide a proper automatic steering method for performing turning travel using two arcs, in a small space as possible, and without damaging a ground surface.SOLUTION: An automatic steering system for a field work vehicle which enters an approach destination travel route Lm from an approach source travel path Ln through turning travel by automatic travel, comprises； an initial turning route calculation part for calculating an initial turning route C1 for initial turning travel subsequent to travel which is along the approach source travel route Ln； a latter period turning route calculation part for calculating a latter period turning route C2 for latter period turning travel subsequent to travel which is along the initial turning route； and an approach route calculation part for calculating an approach route Lin which connects the latter period turning route C2 and the approach destination travel route Lm, in which a turning radius R of the initial turning route C1 is set to be larger than that of the latter period turning route C2.SELECTED DRAWING: Figure 10【課題】２つの円弧を用いた旋回走行を、できるだけ少ないスペースで、かつ地面を荒らさずに行うための適切な自動操舵手法の提供。【解決手段】自動走行によって進入元走行経路Ｌｎから旋回走行を介して進入先走行経路Ｌｍに進入する圃場作業車のための自動操舵システムは、進入元走行経路Ｌｎに沿った走行に続く初期旋回走行のための初期旋回経路Ｃ１を算出する初期旋回経路算出部と、初期旋回経路に沿った走行に続く後期旋回走行のための後期旋回経路Ｃ２を算出する後期旋回経路算出部と後期旋回経路Ｃ２と進入先走行経路Ｌｍとをつなぐ進入経路Ｌinを算出する進入経路算出部とを備え、初期旋回経路Ｃ１の旋回半径Ｒは、後期旋回経路Ｃ２の旋回半径より大きく設定されている。【選択図】図１０
