The present invention relates to a motor drive apparatus and a method of detecting phase currents of a three-phase brushless motor, and, more specifically, to a technique of detecting each phase current with one A/D conversion in one cycle of a PWM carrier using an electric current detector which detects a DC bus current of an inverter. A control unit according to the present invention determines, from the output of the electric current detector, the one phase current with the greatest absolute value at one detection timing in one cycle of PWM control, and estimates the remaining two phase currents on the basis of the peak value of the phase current detected at the detection timing, a motor angle, and a phase displacement of an actual phase current waveform with respect to the motor angle.