An automatic steering system for a work vehicle that automatically travels along a predetermined travel route on a work site, comprising: a steering travel apparatus for performing leftward turning based on a leftward steering amount with respect to a straight-forward direction and performing rightward turning based on a rightward steering amount with respect to the straight-forward direction; a subject vehicle location calculator for calculating a location of a subject vehicle; a locational shifting calculator for calculating locational shifting from the travel route and the location of the subject vehicle; a vehicle body direction calculator for calculating a vehicle body direction that indicates a direction of a vehicle body; a directional shifting calculator for calculating directional shifting from the travel route and the vehicle body direction; a steering amount calculator for calculating a first steering amount, which is the steering amount for correcting the locational shifting and the directional shifting, based on the locational shifting and the directional shifting; and a steering amount limiter for limiting the first steering amount based on a second steering amount, which is the steering amount at present; characterized in that, in response to the second steering amount being the leftward steering amount, the steering amount limiter is configured to limit the first steering amount to the leftward steering amount and a neutral position, and in that, in response to the second steering amount being the rightward steering amount, the steering amount limiter is configured to limit the first steering amount to the rightward steering amount and the neutral position. a steering travel apparatus for performing leftward turning based on a leftward steering amount with respect to a straight-forward direction and performing rightward turning based on a rightward steering amount with respect to the straight-forward direction; a subject vehicle location calculator for calculating a location of a subject vehicle; a locational shifting calculator for calculating locational shifting from the travel route and the location of the subject vehicle; a vehicle body direction calculator for calculating a vehicle body direction that indicates a direction of a vehicle body; a directional shifting calculator for calculating directional shifting from the travel route and the vehicle body direction; a steering amount calculator for calculating a first steering amount, which is the steering amount for correcting the locational shifting and the directional shifting, based on the locational shifting and the directional shifting; and a steering amount limiter for limiting the first steering amount based on a second steering amount, which is the steering amount at present; characterized in that, in response to the second steering amount being the leftward steering amount, the steering amount limiter is configured to limit the first steering amount to the leftward steering amount and a neutral position, and in that, in response to the second steering amount being the rightward steering amount, the steering amount limiter is configured to limit the first steering amount to the rightward steering amount and the neutral position.