The invention relates to the field of automatic welding, in particular to an automatic welder for the impulse welding of an elbow, which comprises a stander, an oscillating body, a roller set, a driver and an electric welder head, wherein the oscillating body is in a fan shape, the circle center of the oscillating body is fixed on the stander, the roller set is arranged along the trajectory of the external circular arc of the oscillating body on the stander and rotates under the driving of the driver, and the oscillating body is provided with a clamping mechanism. The roller set driving the oscillating body of the invention is arranged on the outmost edge of the circular arc to enable the driving force arm to be the longest, and under the function of the same driving force, the maximum torque can be generated. The invention can obtain the effect of low power consumption but high quality under the condition of driving the elbow of high weight, well solves the defects of non-uniform rotary speed and unstable stability of the position limitation, really and effectively guarantees safe work, uses the structure of the oscillating body for driving the elbow to oscillate, and can weld two welding seams in one period.