A device for detecting synchronous errors of high-lift surfaces such as landing flaps or slats on aircraft, having an optical conductor which is laid over at least two adjacent high-lift surfaces, a light source and an optical receiver which are allocated to different ends of the optical conductor, as well as an evaluation unit for determining a synchronous error of the high-lift surfaces on the basis of the light signal received from the optical receiver. The optical conductor is laid in such a way that the optical conductor experiences a break-free deformation due to synchronous errors and consequently causes a change of the transmitted light signals, and the evaluation unit compares the signal shape of the light signal received from the optical receiver or an optical receiver output signal derived therefrom with a nominal signal shape and determines the presence of a synchronous error on the basis of the deviation in shape between the received light signal or the optical receiver output signal derived therefrom and the nominal signal.