A motor drive device of the present invention includes a speed signal generator that generates a rotation speed signal indicating rotation speed; a PWM signal generator that acts on the power switch unit to control the power switch unit so as to generate coil-applied voltage; and a phase advance information generator that has characteristic curve information representing changes of rotation speed of and load on a brushless motor, preliminarily set. The phase advance information generator generates phase advance information according to the load characteristic curve to variably control the phase advance (the phase of voltage applied to the coils of the brushless motor, relative to the induced voltage phase) according to the load characteristic curve.