A control method for brushless DC motor having a rotor, a plurality of magnetic poles and coils of a plurality of phases involves sequentially applying a current to one phase for a prescribed time, stopping the current temporarily and then reapplying the current to the same phase. The state of the rise of the current when it begins to flow to the phase, is measured. The position of one of the magnetic poles located at a position opposite to the particular phase is detected based on the measured state of the rise of the current. In response to the position of the magnetic pole, it is determined whether the flow of the current is to be switched over to the following phase or not. If so, the current is switched over the following phase and the process is repeated. Constant speed control may be accomplished by reading information from a driven disk to determine speed, comparing the speed to a fixed speed, and selectively applying by time sharing a normal current, a brake current and an acceleration current.