The invention provides a laminate board welder and a welding method thereof. The laminate board welder comprises two welders which are arranged in parallel and a positioning base, wherein each weldercomprises a welding box main body, an upper supporting arm, a lower supporting arm, an upper welding head, an upper welding electrode and a lower welding electrode, the upper supporting arm is fixedlyconnected to the top end of the front side surface of the welding box, the lower supporting arm is fixedly connected to the front side surface of the welding box main body and is positioned on a predetermined position below the upper supporting arm, the upper welding head can be arranged on the upper supporting arm in a liftable mode, the upper welding electrode is mounted at the bottom end of the upper welding head, the lower welding electrode is fixedly connected onto the lower supporting arm, and corresponds to the upper welding electrode in position, and the positioning base can be mounted on the lower supporting arms of the two welders in a length direction of the upper welding electrode in a sliding mode, so that a clamping strip can be welded in sections. The laminate board weldercan realize automatic welding of the laminate boards, and facilitates improving welding efficiency and welding quality.