In this paper, a trafficability analysis for the exploration rover is described. A rover traveling on loose terrain often experiences its slippages (wheel slips or vehicle sideslip), and in particular, these slips become larger when the rover traverses on sandy slopes. The authors have investigated traction mechanics of a rigid wheel of the rover on loose terrain with paying attention to slipping behaviors of the wheel. In this paper, based on our previous works regarding the wheel-terrain mechanics, we propose a Thrust-Cornering Characteristic Diagram for trafficability analyses of the rover. The thrust-cornering characteristic diagram consists of various characteristics curves of wheel forces, namely thrust and cornering forces, with various wheel slippage conditions. This diagram provides quantitative criteria for slope traversing capability of the rover on arbitrary angles of slope. The usefulness of the proposed diagram for the trafficability analysis is confirmed through slope traversal experiments using a four-wheel test bed. Further, a steering maneuver control for slope traversing situation is discussed based on the diagram.