A seat adjusting device for an automobile seat (1) having an electric motor (11) for generating a drive motion, wherein the electric motor is operationally coupled to a gearbox (13) for transmitting the drive motion thereof, the gearbox having a gearbox housing (19) in which gearbox elements are disposed for a step-up or step-down transmission of the motor drive motion, by means of which electric motors of lesser technical complexity can be used than previously. To this end, the invention proposes that the gearbox (13) has detection device for detecting information about the speed of at least one of the gearbox elements or detecting a variable dependent on the speed.