The invention relates to a welding method and a welding device of a complex curved surface vehicle lamp. The welding method comprises the following steps that according to the material of the vehicle lamp to be welded and the curvature of a curved surface of the vehicle lamp, welding parameters of the complex curved surface vehicle lamp to be welded are set in a laser generator; a lamp body to be welded and a light-distributing lens are driven by an air cylinder to be in contact with a transparent pressing film; the transparent pressing film tightly compresses the lamp body and the transparent pressing film, wherein the transparent pressing film and the light-distributing lens are consistent in shape; the laser generator is started, and the laser generator generates laser beams with different powers according to the set welding parameters, the material of the complex curved surface vehicle lamp and the curvatures of different curved surface positions of the vehicle lamp to be welded; after the laser beams are subject to light condensation through the transparent pressing film, welding along a welding part is performed according to set welding speed. The welding method is very low in energy consumption, environment pollution is not caused, and the problems that the current welding method of the complex curved surface vehicle lamp is relatively high in energy consumption and poor in welding quality and causes environment pollution are solved.