Electrical steel sheets, which are used in real rotating machinery, are magnetized under alternating and rotating magnetic flux conditions. In addition, the magnetic properties of the electrical steel sheets are strongly affected by stress. Therefore, it is important to understand the magnetic properties under different mechanical stress and magnetic flux conditions, that are based on phenomenon in the real rotating machinery. This paper presents the effect of stress on the vector magnetic property under the rotating magnetic flux conditions with a developed measurement system. We investigate the behavior of the vector magnetic property of a nonoriented electrical steel under the rotating magnetic flux condition by applying mechanical stress along the rolling direction.