This invention relates to a motor control method and a control apparatus therefor in which an electric motor driven by a pulse width modulation inverter is digitally controlled by a digital arithmetic and logic circuit. Register file means including reference register groups, instantaneous register groups, comparison circuits and comparison output latch groups controlled in a time division mode by a stage signal is composed of a plurality of register files and the number of processing frequencies in response to the stage signal is increased, so that the motor can be controlled by a pulse width modulation signal having a fundamental wave frequency ensuring a higher resolution.