An adjustment device for adjusting several guide vanes of the engine, wherein the adjustment device includes at least one adjusting element that couples with the guide vanes and is mounted in an adjustable manner, a connection element that couples with the adjusting element, as well as a crank shaft for controlling an adjusting movement of the adjusting element, and the crank shaft has at least one coupling element which couples with the connection element and at which the connection element is hinged to transform a rotational movement of the crank shaft about a longitudinal axis of the crank shaft into an adjusting movement of the adjusting element for adjusting the guide vanes. The crank shaft has a modular design with at least two shaft modules that are arranged behind each other along the longitudinal axis of the crank shaft.