A process of cladding by welding includes the steps of: (1) preparing a workpiece having a cladding-scheduled portion including an exposed normal region, the exposed normal region having a normal surface including a possibility that a foreign substance portion exists, and the foreign substance portion to form a defect of cladding; (2) irradiating the exposed region of the cladding-scheduled portion of the workpiece with an high-density energy beam, the high-density energy beam capable of eliminating or decreasing the foreign substance portion, substantially without melting the exposed normal region of the cladding-scheduled portion; and (3) covering the exposed normal region of the cladding-scheduled portion of the workpiece with a clad layer.