An electric motor system includes a rotary shaft having an axis line displaceable relative to a rotation center, a magnetic bearing for supporting the rotary shaft, a permanent magnet mounted on the rotary shaft and having a plurality of magnetic poles arranged in a circumferential direction around the axis line of the rotary shaft, three detection elements arranged in the circumferential direction around the rotation center for detecting a magnetic flux generated from the permanent magnet, and a coordinate detection section for determining coordinates of the axis line of the rotary shaft based on output values of two detection elements selected out of the three detection elements in accordance with a rotation angle of the rotary shaft.