Wall-climbing robots can be used for some tasks such as painting, inspecting and cleaning of various walls. The typical wall-climbing robots use a magnet or a vacuum suction device for attracting with the wall. For a reliable task, the robots should follow a desired path accurately. However, the trajectory tracking on the vertical wall is not easy because of gravitational and attraction force. In this paper, a trajectory tracking control for a skid steer type wall-climbing robot is proposed. The control law is a non-linear feedback one with a compensation of gravity and attraction force. A window cleaning robot is used for an experiment of the trajectory tracking control. The experimental result confirms the validity of the proposed method.