A detection device for detecting a magnetic pole position of a synchronous motor includes a generating unit for generating a magnetic pole correction value based on the difference between a forward rotation d-phase voltage command and a reverse rotation d-phase voltage command, the d-phase voltage commands being used for rotating the synchronous motor and generated when the synchronous motor is driven in forward and reverse directions, respectively, by applying a prescribed d-phase current command after detecting a magnetic pole initial position at power-on of the synchronous motor, and a correcting unit for correcting the magnetic pole initial position based on the magnetic pole correction value and on a sensor reference position which defines a reference position of a sensor attached to the synchronous motor, and a control apparatus equipped with the detection device controls the rotation of the synchronous motor based on the corrected magnetic pole initial position.