To reduce information used for processes of complementing a missing detection pulse of a magnetic field detecting section, the apparatus carries out the processes of storing, as rotation direction information of a movable section 43, “rightward direction”, “leftward direction”, “unidentified” and “unidentified inversion”, and setting the rotation direction information to “unidentified” when recognizing a missing detection pulse, and subsequently, adjusting a rotation change amount of the movable section using a first adjustment value if the rotation direction information becomes the “unidentified” and adjusting the rotation change amount of the movable section using a second adjustment value if the rotation direction information is updated from the “unidentified” to the “rightward direction” or the “leftward direction”.