This paper describes the development of a tire testing machine with 6-degree-of-freedom motion system. Vehicle behavior depends on cornering force, which arises on tire. Vertical load of tire and its alignments change while vehicle is moving on road, and it causes a change of cornering force. To evaluate influence of vertical load of tire and its alignments change, we developed a tire testing machine with 6-degree-of-freedom motion system. The developed testing machine consists of motion system, suspension mechanism, and roller conveyer. With the developed testing machine, influence of a change of vertical load of tire and its alignments on tire was evaluated.