The invention relates to the technical field of electronic equipment, and discloses a welding device and welding method for a printed board assembly based on inter-board vertical interconnection. The welding device comprises a positioning plate, a supporting plate, pins and screws, wherein the positioning plate is arranged above a printed board, the supporting plate is arranged below the printed board, the positioning plate, the supporting plate and the printed board are positioned through the pins, and the positioning plate, the supporting plate and the printed board are fixed together through the screws. According to the welding device and welding method, the welding device is adopted to mount and position a surface-mounted connector on the printed board assembly, the buckling deformation of the printed board in the welding process is controlled, accurate positioning and reliable welding of the surface-mounted connector based on inter-board vertical interconnection are realized, the problems of the position offset of the surface-mounted connector on the printed board assembly, the inclination and flotation of the connector and the buckling deformation of the printed board can be solved, and therefore the realizability and reliability of inter-board vertical interconnection are improved.