The invention relates to the field of resistance welding, in particular to an automatic circuit board welding machine which comprises a machine body, a conveying device, a rotating plate, a welding device and a cutting pin device. The conveying device and the rotating plate are installed on the machine body, the welding device and the cutting pin device are installed on the rotating plate, the conveying device comprises a conveying belt, the conveying belt is provided with board placing grids capable of being used for placing circuit boards, the sizes and number of the board placing grids on the conveying belt are adjustable, and thus the automatic circuit board welding machine adapts to placement of circuit boards with different sizes and different numbers. The number of the welding devices installed on the rotating plate can be adjusted according to the number of the board placing grids, the cutting pin device is used for overturning the whole well welded circuit boards, and redundant pins of well welded electronic elements are removed. According to the automatic circuit board welding machine, full-automatic soldering and full-automatic pin removal and the like can be performed on different types and different numbers of circuit boards.