PURPOSE: To prevent the deformation of the lead frame generated when sealed with resin by forming a notch to the frame base section of a unit lead frame in the direction crossing with the longitudinal direction.

CONSTITUTION: One notches 38 shaped to the frame base section 36 from the outsides toward other end surfaces from the end surfaces of the frame base section and two ones from the lead side at the inside are alternately formed in parallel and in bilateral symmetrical shape in the frame of the unit lead frame. The width of the notches may be approximately treble of the thickness of the lead frame, length and extent exceeding the center of the width of the frame base section 36, the mutual shortest distance approximately treble of plate thickness and the number of the notches approximately three. When the lead frame according to this constitution is sealed with resin, the notches are expanded and contracted to external stress due to the shrinkage of the resin, the frame base section is deformed only in the longitudinal direction of the lead frame, compressive stress generated at the frame base section is buffered while the tensile stress of external connecting leads is also buffered simultaneously, and deformation is completely prevented.