A resin material supply apparatus and a method thereof ensuring the supply of a predetermined amount of resin material and improved molding quality. The resin material supply apparatus includes a weighing unit which allows a predetermined amount of resin material to be loaded into weighing pots, an agitating unit which receives the resin material from the weighing pots into agitating cups for agitation using rotating plungers, a traveling unit which allows the agitating unit to travel back and forth between the weighing unit and a molding die, and a supply unit which permits resin material which has been agitated and molten in the agitating cups to be extruded into a mold pot of the molding die by movement of the plungers via a vertically traveling motor rotatable in both forward and reverse directions.