A control unit for an induction motor continuously provides a precise output torque without being adversely affected by a magnetic saturation of an iron core, or varying precision of sizes of components constituting the motor or varying temperature of the motor. When a torque command value T* is smaller than a predetermined value Trf, an excitation inductance M is corrected in accordance with a torque voltage command Gq.multidot..DELTA.i1q which is calculated on the basis of a torque current command i1q* and a torque current i1q. Further, a secondary resistance r2 is corrected on the basis of the torque voltage command G.multidot..DELTA.i1q. A slip frequency is calculated on the basis of the secondary resistance r2, a magnetic induction command .phi.*, and torque current command i1q*. An angular frequency command .omega. is calculated. The magnetic induction command .omega.* and the torque command T* are converted into an excitation voltage command ed* and torque voltage command eq* to be applied to the motor on the basis of the corrected excitation inductance M and the angular frequency command .omega..