To improve traveling stability by adjusting a front wheel to an inter- ridge position by striding over a ridge by left/right rear wheels and laterlally rotating a front frame, by longitudinally dividing a machine body frame in a midway part, and laterally rotatably connecting a rear part of the front frame in a rear frame front part.

A front wheel 2 of one wheel is supported in a machine body frame front part, and rear wheels 3, 3 of two wheels are supported in a rear part to constitute a three-wheeled driving vehicle. A machine body frame is formed in a step difference shape in a longitudinal directional almost central position, the front side is formed as a front wheel frame 1a, and the rear side is formed as a rear frame. The front wheel frame 1a is laterally rotatably supported, and a work machine frame 1c is projected forward from the lower part. A front case 7 is fixed to a front part of the front wheel frame 1a, and the front wheel 2 is supported in the lower part via a front wheel driving case. A work machine 40 is suspended by a work machine frame 1c to be thereby guided to a proper place of a rice field to reliably perform husbandry work.