PURPOSE: To execute positioning at a high speed and with high accuracy, by providing an actuator base so as to pass through the center of gravity of a housing, and also making a point of application of a voice coil coincide with the position of the center of gravity of a carriage.

CONSTITUTION: An actuator base 1e is fixed so as to pass through the height of the center of gravity of a rectangular housing, onto which a pickup 6 and optical parts are fitted, and a mass distribution of a carriage is centralized around the base 1e. Also, a driving voice coil 7 is fitted to both sides of the carriage center part so that a point of application of resultant force of two driving forces nearly coincides with the center of gravity A of the carriage. This carriage is driven through a bearing 2 and a guide rail 3, but since its driving force always operates on the center of gravity, harmful pitching vibration and resonance are prevented, and positioning is execuated at a high speed and with high accuracy.