When a slope tractor works on the slope land, it travels usually along the contour and slope line. In that case, the efficiency of work generally decreases and the safety of the operator caused by the overturn of the tractor should be considered. Maintaining the tractor body being horizontal during the travel is crucial to solve problems. To overcome such a problem, an automatic leveling control system for slope tractor has been developed. The system composed of sensor for measuring rolling and pitching inclination of the slope tractor chassis, controller, hydraulic control system and mechanism. The limit angle of the leveling control was set up to be ${pm}15^{circ}C$ for rolling, ${pm}7^{circ}C$ for pitching. The proposed control and hydraulic power system was implemented to the prototype slope tractor. This paper shows results about development of the automatic leveling mechanism and response properties for slope tractor.