PROBLEM TO BE SOLVED: To provide a traveling work machine which, while adopting manual steering and automatic steering, can make efficient work possible without causing burdens on an operator, and an automatic steering system used therein.SOLUTION: A traveling work machine and an automatic steering system used therein comprise: a position unit 5 for outputting positioning data indicating the position of the work machine a route calculation unit 81 for calculating a target traveling route a direction calculation unit 84 for calculating the direction of a traveling machine 1 relative to the target traveling route on the basis of the positioning data a steering data output unit 82 for outputting automatic steering data in order for traveling along the target traveling route an automatic steering unit 83 for generating a steering signal in order for steering the traveling machine 1 on the basis of the automatic steering data and an automatic steering management unit 85 which, in a shift from traveling by manual steering to traveling by automatic steering, disables shifting to automatic travelling by the automatic traveling unit 83 as long as the direction of the traveling machine 1 calculated by the direction calculation unit 84 exceeds a prescribed permissible range.SELECTED DRAWING: Figure 1
