PURPOSE: To settle disadvantages, such as contact-pressure drop, as a conductive spring material, by subjecting an age-hardening alloy after workings such as surface grinding to leveler treatment by means of a roller leveler so as to recover elastic limit value.

CONSTITUTION: Leveler treatment is applied by means of a roller leveler to an age-hardening alloy which is passed, if necessary, through solution heat treatment, cold rolling, and age-hardening treatment stages and then subjected to surface grinding and cutting and/or plastic working. By this method, deteriora tion in elastic limit value based on the residual stress to working is recovered, so that the above-mentioned alloy minimal in the deterioration in elastic limit value can be obtained.