A motor drive device for alternately driving a plurality of motors includes a position detection signal processing circuit for processing position detection signals of the plurality of motors, a pre-drive circuit for generating an excitation switching signal of the motors, a plurality of power switching circuits for supplying an electric current to the motors in response to an output from the pre-drive circuit, and a motor switching circuit for instructing a switchover of driving the motors. The position detection signal processing circuit, in response to an input signal to the motor switching circuit, selects a position detection signal of a motor to be driven out of the position detection signals of the plurality of motors, and inputs a position detection processed signal to the pre-drive circuit for selecting one of the plurality of power switching circuits.