To provide a high-performance, a high-power motor drive controller, and an electric power steering device by reducing the task load on a microcomputer and enabling the computation of an n-phase current detection correction value.

A current controller 35 is so constructed that n-phase current controller computation and n-1-phase current controller computation is replaced with each other. In computing a current detection correction value, n-phase current controller computation is carried out to compute an n-phase current detection correction value and obtain an accurate n-phase current detection value. In normal control in which current detection correction value computation is not carried out, n-1-phase current controller computation is carried out. In this n-1-phase current controller computation, an n-1-phase voltage command value is computed based on an n-1-phase current command value and an n-1-phase driving current detection value. In addition, a voltage command value of the remaining one phase is computed based on the n-1-phase voltage command value.