In a moving magnet type linear motor including a stator with a plurality of coils placed in one direction and a mover with a permanent magnet opposed to the stator, a position detector detects the position of the mover. The position detector includes a magnetic body fixed to the mover. One or two or more coils are selected and a voltage is applied to the selected coil while a current or a voltage induced in a coil adjacent to the selected coil is measured, and the position of the magnetic body that changes in response to the position of the mover is determined based on the measured current or the measured voltage.