The invention relates to the field of shipbuilding welding devices, in particular to a split splicing welding device for hull building. The split splicing welding device comprises a base used for containing a hull, the base is provided with a splicing device which is used for supporting the hull and controlling the transverse movement of the hull to complete splicing, and a welding device used foradjusting the welding position according to the transverse movement and the splicing position of the hull is arranged beside the splicing device. The hull can be automatically spliced by means of theinclination force, and manual pushing which wastes time and labor is not needed, so that the working efficiency is improved; a step column is used for limiting and effective lifting, and compared with traditional welding which needs accurate positioning, the working time is shortened; and three welding directions are available, so that the flexibility is high.