This paper describes the magnetostriction of an arbitrary direction under an alternating magnetic flux measured by a two-dimensional magnetic measurement method. The magnetostriction of an arbitrary direction was measured by three-axial strain gage and analyzed by the tensor method. In the case of non-oriented silicon steel sheets, the magnetostriction in a direction 45 degrees from the rolling direction was larger than in the rolling direction. In the case of grain-oriented silicon steel sheets, the magnetostriction in a direction 90 degrees from the rolling direction was larger than in the rolling direction.