Object of the present invention is to provide a lens driving unit in small size and perform a high ratio optical zooming and a lens driving device. To achieve the object, the lens driving unit in which the lens group holding frame supported to be able to slide by connecting to a guide pole arranged in parallel with the optical axis; and a drive transmission unit consisting of a pinion mounted on the output shaft of the motor and a rack formed in the lens group holding frame is adopted, and a driving force of the motor is transmitted to the lens group holding frame by gearing the pinion with the rack to make the lens group holding frame slide along the guide pole, and a lens driving device comprising the lens driving unit is adopted.