PROBLEM TO BE SOLVED: To enable a gauge wheel unit, including a gauge wheel attached at a rear end side part of a reverse frame of a field work machine, to be easily switched into appropriate states when working while travelling in a not-plowed field and when working while travelling in a plowed floor after plowing-up, respectively.SOLUTION: A gauge wheel unit 45 includes: a mounting part 49 mounted rotatably to an attachment frame and a gauge wheel 46 regulated in vertical movement in a predetermined range by regulation means and enabling a vertical position adjustment. When the gauge wheel unit is switched from working while traveling in a not-plowed field to working while traveling on a plowed floor after plowing-up, the whole gauge wheel unit 45 is rotated with an attachment shaft extended in front/rear direction of the attachment frame as the center, and the gauge wheel 46 is arranged while located downward by self-weight without being regulated in vertical rotation by the regulation means.
