Discussed is a battery module manufacturing system, which includes a battery module having a cell stack formed by stacking a plurality of battery cells, a module case configured to accommodate the cell stack and a bus bar frame configured to cover an opening at one side of the module case; a fixing frame coupled to one side of the battery module so that the bus bar frame is exposed to the outside; and at least one pressing jig apparatus coupled onto the fixing frame and configured to press electrode leads of the plurality of battery cells so that the electrode leads are welded in close contact with both sides of a bus bar provided to the bus bar frame.