A position controller provided in a controlling module obtains a difference between a detected rotation angle of a stylus and a target rotation angle, and determines an energization amount to a voice coil motor so that the difference becomes zero. A variable limiter circuit limits a driving current, which is supplied from the position controller, to a limitation value so that a rotation force applied to the stylus from the voice coil motor is constant. A target rotation angle issuing portion switches over the target rotation angle based on a relative position of a contact portion of the stylus.