The invention discloses a mobile phone frame and middle plate automatic welding device. A welding jig with a frame correcting plate is designed, and the frame correcting plate is located between the jig base and the welding cover plate; the device comprises a rectangular pushing block and four rectangular plates, wherein the rectangular pushing block is composed of two outer pushing blocks, and the four rectangular plates are arranged around the rectangular pushing block; an air cylinder device on the jig base is connected with the two outer pushing blocks and drives the two outer pushing blocks to move in the length direction and the width direction of the rectangular pushing blocks; gaps between the four rectangular plates and the rectangular pushing blocks are spliced to form a rectangle, and the mobile phone frame is placed in the gaps; the air cylinder device drives the two outer pushing blocks to move in the length direction and the width direction of the rectangular pushing block, the outer rectangular plates are matched to make the two sides of the frame be extruded, and then middle plates are pressed on the frame by being matched with a welding cover plate; the mobile phone frame and the middle plate are welded, and the mechanization is accurate relative to manual operation; and the yield of the product is greatly improved, the labor cost is saved, and the production efficiency is improved.