The disclosure relates to a magnetic device for detecting the absolute position of an input shaft capable of rotating more than 360°, the device including a main magnetic sensor, a motion reducer, and a secondary magnetic sensor, wherein the main magnetic sensor is connected to a rotor, measures the rotation of the shaft for ranges of angles of less than 360°, and includes a main magnet, the motion reducer converts the rotation of the shaft into a reduced rotation, the maximum amplitude of which is equal to no more than 360°, and the secondary magnetic sensor measures the reduced rotation and includes a secondary magnet. According to the disclosure, the secondary magnet is arranged between the upper and lower planes of the main rotor, and the main magnet has P pairs of poles, where P is greater than 1.