This work deals with a motion planning algorithm of an omni-directional mobile robot with active caster wheels. A typical problem occurred in the motion control, which has been identified through experimental experiences, is skidding of the mobile wheel. It sometimes results in uncertain rotation of the steering wheel. This is due to mismatching between the command and the mechanical hardware. To cope with this problem, a motion planning algorithm pursuing the natural configuration of the mobile wheel was mainly investigated, which resolves the skidding problem and uncertain motions of the steering wheel. Through simulations and experimentation, the feasibility of this algorithm was verified.