Abstract: A four-wheel drive tractor is provided with a front-wheel driving mechanism according to the invention, a universal joint is interposed in a portion of the front-wheel drive shaft system which carries out the front-wheel drive and intersects with the center axis of the kingpin. A universal joint housing encloses the universal joint and is divided into upper and lower parts along a plane perpendicular to the center axis of the kingpin, and the lower universal joint housing part is interlocked with a yoke and is pivotable in relation to the upper universal joint housing part together with the front wheels.