A method for controlling a brushless DC motor including steps of detecting a rotation speed and rotor position of a brushless DC motor (803, 913) excited by a voltage-fed inverter (802, 912), characterized by the steps of: setting an amplitude of output voltage of the voltage-fed inverter (802, 912) in a specified amplitude that is determined based on the detected rotation speed and set in response to a difference between an order rotational speed given to the brushless DC motor (803, 913) and the detected rotation speed a switching command to the voltage-fed inverter (802, 912) such that the phase relative to the counter electromotive voltage of the motor is set in a specific phase and such that a terminal lead width voltage fed inverter (802, 912) is set to 180 ° in electrical angles.