A method for manufacturing a molybdenum sputtering target for a back electrode of a CIGS solar cell is provided to minimize thermal activating reaction by employing an electric discharge plasma sintering process. The method for manufacturing a molybdenum sputtering target for a back electrode of a CIGS solar cell comprises the steps of: charging molybdenum powder in a mold of graphite material, mounting the mold in a chamber of an electric discharge sintering apparatus, making a vacuum in the chamber, forming the molybdenum powder to the final target temperature while maintaining constant pressure on the molybdenum powder, heating the molybdenum powder in a predetermined heating pattern when reaching the final target temperature, maintaining the final target temperature for 1 to 10 minutes, and cooling the inside of the chamber while maintaining a constant pressure.