Output reduced by a reduction mechanism A contained within a tube type motor body 5 is transmitted to a threaded shaft 13, and a nut 15 having a wing element 15a for transforming rotation of the threaded shaft 13 to propulsion is threadingly engaged with the threaded shaft 13. Then, reduction and boost is made between a linear groove 16a of a guide member 16 secured to an inner wall of the body 5 and the rotation is transmitted to the body 5 by this rotational force, thereby an arm 17 provided on the body 5 is swung so that a base 3 is adjusted upwardly and downwardly about bearing members 2, 2a mounted on slide rails 1, 1. Owing to this arrangement, since a smaller installation space can be achieved, the apparatus can be made small in size and commonly used for various types of automotive vehicles. Moreover, the apparatus can be unitized. In addition, a high torque transmission is made possible by reduction and boost.