Abstract: An adjusting device for an automobile seat having a back, a seating part formed by a seat substructure and a seat cushion, and with a side part that is guided horizontally by means of rails. The adjusting device can selectively regulate the seating part with respect to height, leaning or longitudinal distance. The adjusting device is formed by at least one fixed planetary gear system with a rotation drive device associated with, for example the seat substructure, the side part or seat rail and placed in a gear box casing. The planetary gear system has at least one sun wheel, one planet wheel and one ring gear respectively. The sun wheel interacts with the rotation driving device to operate the adjusting device.