The present invention relates to a lens driving device includes a lens receiving part with a lens disposed therein, having first and second extension parts formed at opposed sides in a predetermined interval from each other. The lens driving device also includes an actuator having a body between the first and second extension parts. The actuator body has first and second output members contacting the first and second extension parts of the lens receiving part at opposed ends thereof, and thereby expands, contracts and bends when power is applied. The lens driving device also includes a preload member compressing the first and second extension parts against the actuator body to maintain a status of pressed contact. The lens driving device further includes a guide part for guiding the movement of the lens receiving part in an optical axis direction.