The invention discloses a device and a method for welding electrode plates of cylindrical batteries. The device for welding the electrode plates comprises two clamp plates, at least two positioning columns and positioning nails. The two clamp plates are oppositely arranged at preset intervals, positioning protrusions which are matched with center tubes of the batteries are arranged on opposite surfaces of the two clamp plates, and at least two positioning holes and a plurality of laser holes are formed in each clamp plate; the positioning columns are arranged between the two clamp plates, two ends of each positioning column are respectively inserted into the corresponding positioning holes of the two clamp plates, and screw holes are formed in the two ends of each positioning column; the corresponding positioning nails can penetrate the corresponding positioning holes to be connected with the screw holes in the two ends of each positioning column in a threaded manner, so that the positioning columns can be fixedly connected with the two clamp plates. The device and the method for welding the electrode plates of the cylindrical batteries have the advantages that effects of tightly connecting the positive electrode plates and the negative electrode plates with the end surfaces of battery cells can be realized, the problem of defects such as pseudo welding can be solved, the device and the method can be widely applied to mass production, and the device is simple in structure and easy to operate.