The invention relates to a laser cladding forming device and a laser cladding forming method of a metal part. The device comprises a work bench in three-dimensional motion, a laser device, a wire feed device and a control system, wherein the wire feed device comprises a pinch roll wheel set, and the drive wheel of the pinch roll wheel set is connected with a stepping motor; the control system comprises a multi-shaft motion control card, and the multi-shaft motion control card is connected with the stepping motor, a work bench driving motor and the laser device respectively. The method comprises the steps of modeling, instruction conversion, sheet forming and deposition forming and the like. Metal wires are molten by laser to form molten drops, the molten drops are piled up and cooled on the work bench, sheets are formed along with the motion of the work bench, and all sheets are deposited layer by layer to form the three-dimensional metal part. The invention has low manufacturing cost, high forming efficiency, high part structure strength, high surface quality and wide application range.