To provide a positioner which allows a reduction in fluctuation in speed.

Teeth on a slider portion 2 side and teeth 3a on a grid platen 3 side are mechanically formed with accuracy. Therefore, relation between cogging force and commutation angle is substantially uniform throughout a motion space. When an X-axis position speed control portion 20 drives X-axis motors 4 and 5 at constant speed, a correction table storing portion 42 stores a fluctuation component (AC component) in an X-axis current command value as an X-axis current correction value corresponding to the X-axis commutation angle of the X-axis motors 4 and 5. When the X-axis motors 4 and 5 are driven by a command from a higher level controller 18 during run proper, an X-axis current correcting portion 44 periodically reads an X-axis current correction value corresponding to the X-axis commutation angle out of the correction table storing means 42, and adds the correction value to the X-axis current command value. As a result, a fluctuation in speed due to cogging force can be reduced.