The invention discloses a rail joint transverse dislocation detection device and method. The detection device comprises at least two distance-measuring sensors; the distance-measuring sensors are arranged on side faces of a steel rail; the distance-measuring sensors are used for detecting a transverse distance between the steel rail and the distance-measuring sensors; the distance-measuring sensors are fixedly mounted on a sleeper (6) or a base (7) of the rail. The detection method comprises: mounting the rail joint transverse dislocation detection device; carrying out reference measurement and calculating a reference transverse distance difference; carrying out dislocation detection and calculating an instant transverse distance difference; comparing numerical values of the reference transverse distance difference and the instant transverse distance difference and analyzing dislocation. After the device disclosed by the invention is mounted, real-time detection can be realized; the detection process does not influence the normal running of a train and the utilization is convenient and safe. By detecting the distance between the sensors with the fixed positions and the steel rail, transverse dislocation of the steel rail is judged and a detection result is reliable and has high precision. Dynamic and remote rail joint dislocation detection can be realized so that the rail joint transverse dislocation detection device and method can be applied to large-scale and large-batch detection.