The utility model provides a rail welded joint straightener comprising a rack (4), as well as a first fixed fulcrum part (1), a second fixed fulcrum part (2) and a hydraulic control device which are arranged on the rack (4), wherein the hydraulic control device is connected with a movable fulcrum part (3). The rail welded joint straightener is characterized by also comprising a laser probe and a control box which is used for controlling the hydraulic control device, wherein the laser probe is arranged at a place on the rack (4) near the movable fulcrum part (3), and the laser probe is connected with the control box through a data line. The rail welded joint straightener realizes full-automatic measurement process by equipment, does not need manual intervention, achieves high degree of automation, can effectively reduce the labor intensity of operators and simplify the operation technology; the rail welded joint straightener can measure and display the straightness data of a rail welded joint in real time, thereby providing data basis for the work of the operators and remarkably improving the working efficiency; and the rail welded joint straightener can effectively enhance the measurement precision.