A method for producing a semiconductor device includes: a) an attaching process in which a flat-plate member is positioned on a flat-shape lead frame provided with a plurality of leads and a plurality of support bars so that the flat-plate member contacts at least the plurality of leads, and the flat-plate member is attached to plurality of support bars; b) an element mounting process in which a semiconductor element is mounted on the flat-plate member attached to the plurality of support bars of the flat-shape lead frame; c) a wire-bonding process in which a wire is provided between each of the plurality of leads and the semiconductor element; and d) a separating process, performed after the completion of the wire-bonding process, in which the plurality of support bars are deformed so as to separate the flat-plate member and the plurality of leads and electrically disconnect or separate the flat-plate member from the plurality of leads.