To provide a motor controller which can stabilize motor drive control even in case that sensorless vector control and overmodulation control are combined.

The controller performs sensorless vector control by detecting the current flowing in a motor 45M. In addition, when a modulation rate setter 82 sets a modulation rate M to 1.0 or over and executes overmodulation control, a rotational position estimator 62 smoothes a d-axis induced voltage Ed obtained in the process of positional estimation via a digital filter 84 and estimates its rotational speed e and rotational position e, based on the smoothed d-axis induced voltage.