A cathode roller mechanism comprises a tapered cathode roller for establishing an electrical connection to a semiconductor lead frame and an elastic, frictional pressure roller. The cathode roller comprises a tapered roller body defining a tapered side surface and an electrically conductive stopper disposed on the roller body and having an inner tapered electrode. The pressure roller is arranged so that the path of a drifted lead frame can be corrected, and the drift of the lead frame can be positively prevented by pressing the lead frame in such a manner that no drift of the lead frame occurs. In addition, an auxiliary electrode is provided on the inside of the tapered electrode, a third tapered surface is provided on the auxiliary electrode, and the width of the pressure roller is set to a length sufficient to press a corner of a molded portion of lead frame having the maximum width so that electrical continuity, i.e., the connection between the lead frame and the electrode, can be stabilized, and the lead frame can be more stably made a cathode.