A brushless DC motor configured to drive a driven member includes a rotor having a magnet, a stator having a coil configured to provide a rotational force to the magnet, a position detector configured to output a first signal that is periodic, in accordance with a rotating position of the rotor, a signal generator configured to generate a second signal by adding a lead angle to a phase of the first signal output from the position detector, an excitation switch configured to select an excitation to the coil in accordance with the second signal, and a phase change part configured to change the lead angle in accordance with at least one of a position and a moving direction of the driven member.