Abstract: An internal grinding apparatus having a grinding wheel attached to a spindle rotor radially and axially supported by electromagnetic bearings. Currents applied to the electromagnetic bearings are continuously controlled by a controlling system including a central processing unit during grinding work in order to adjust the longitudinal axis of the spindle rotor. The longitudinal axis of the spindle rotor is inclined and/or shifted at predetermined locations of the grinding wheel in a bore of a workpiece, thereby eliminating tapering of the long bore, and improving the cylindricality and straightness in grinding work.