PURPOSE: To improve the workability, sealability and strength of a lead frame material by subjecting an alloy in which the content of C, Si, Mn, Ni, Cr, Fe or the like is specified to final annealing and final cold rolling under prescribed conditions and thereafter executing stress relieving heat treatment under prescribed temp., time and atmospheric conditions.

CONSTITUTION: An Fe-Ni-Cr alloy constituted of, by weight, ≤0.015% C, 0.001 to 0.15% Si, 0.1 to 1% Mn, ≤0.01% P, ≤0.005% S, ≤0.01% O, ≤0.005% N, 5 to 15% Cr, 33 to 55% Ni and the balance Fe is melted. This alloy is rolled at 40 to 90% draft and is thereafter subjected to final annealing under the condition of ≤30μm grain size. Next, the alloy is subjected to final cold rolling in which its draft is regulated to 40 to 85% and is thereafter subjected to stress relieving heat to 10hr treating time in vacuum or in the atmosphere of an inert gas or the like.