To improve control performance by providing a power computer generating a current setting signal out of the output and the exponent of a divider in which the sum of output of two parameter setters is set as a denominator and torque setting signal input is set as a numerator.

A transfer function G from the set torque τ* of the torque setter 3 at an input point up to the torque τ at an output point is made to be G=1. Hereat, on assumption that this current control system is sufficiently good in the control characteristic, the current control gain 8 is shown to be 1. By setting the torque in this way, it is shown that it becomes the torque as it is. In parameters k1, k2, m in curent conversion, when mechanical parameters and a set parameter (with a hat signal) contain errors, (τ*=τ) is not realized. Hereby, a torque amplifier for correction is provided in parallel with a torque/current converter, and hence accuracy can be insured.