The present invention provides a method for manufacturing a mask frame used for a cathode ray tube, comprising a first step of seating at least two semifinished products on jigs such that corresponding distal ends of the semifinished products are brought into contact with each other to form a closed ring; a second step of feeding the semifinished products seated on the jigs to a welding machine; a third step of welding the plurality of fed semifinished-products into a primary workpiece in the form of the closed ring; a fourth step of feeding the primary workpiece welded in the third step to a brushing device; a fifth step of removing foreign substances adhering to welded portions of the primary workpiece; a sixth step of feeding a secondary workpiece, which has undergone the fifth step, to an applicator device; and a seventh step of applying oil to processed portions of the secondary workpiece formed through the welding and brushing processes to prevent corrosion thereof. The present invention also provides aa welding machine for welding at least two semifinished products into a closed ring; a brushing device for removing foreign substances adhering to welded portions of a primary workpiece made by the welding machine; an applicator device for performing corrosion-resistant processing on processed portions of a secondary workpiece made by the welding machine and the brushing device; and a feeding device for feeding the semifinished products and a finished product to ensure that the welding process, the brushing process and the application process can be performed consecutively. According to the present invention, the productivity of a manufacturing process can be improved by reducing time required for manufacturing a mask frame and by minimizing the amount of material used.