A motor drive control system suitable for control of a drive of a motor, such as a brushless motor or a linear motor, having a plurality of excitation phases, through the use of rectangular waves. A drive means is provided for producing an excitation signal to be supplied to each of the excitation phases of the motor and a control means for determining a direction of the excitation signal for each of the excitation phases and for conducting ON/OFF switching. The control means controls the rate of change of the excitation signal to be switched at the switching operation.