PURPOSE: To reduce maintenance cost and improve quality by setting a burr blow-out position while detecting a positioning hole of a lead frame when performing blow-out by laser light of gate burr.

CONSTITUTION: A lead frame is positioned at a specified position after sealing resin of a semiconductor element and a positioning hole 6 of a lead frame 1 is detected by a sensor 25 to allow the blow-out position of a gate burr to be set. At this time, optical transmission and reception can be performed between a light-emitting element 25a and a light-receiving element 25b. After that, a laser light 22 is irradiated to the blow-out position to allow the gate burr 7 of a mold resin 3 to be blown out. Thus, it is not necessary to replace parts frequency even if the number to be eliminated increases, occurrence of mechanical stress for the mold resin 3 is prevented, and it is not necessary to retain the mold resin 3 by a stripper, etc., when eliminating burr.