This paper proposes a method which enables wheeled robot to climb a step that is higher than the radius of the wheel. In conventional method, the velocity at the moment of impact and impact force must be increased in order to climb the step, which causes troubles of wheeled robot. This paper proposes a method utilizing variable loads arised by changing speed and anti-dive force from suspension to climb the step more safely. Effectiveness of the proposed method is verified by simulations and experiments.