To provide a Cu-Ni-Si-based alloy for electronic material in which addition of other alloying elements can be minimized and yet improved electric conductivity, strength, bendability and stress relaxation characteristics can be combined.

The Cu-Ni-Si-based alloy has a composition consisting of 1.2 to 3.5 mass% Ni, Si in a concentration (mass%) from one-sixth to one-fourth the Ni concentration (mass%), and the balance Cu with 0.05 mass%, in total, of impurities. By controlling solution heat treatment conditions, aging treatment conditions and rolling draft and regulating the shape of a crystal grain and the width of a precipitate free zone each to a proper range, a strip of the copper alloy having the following characteristics can be provided: the electric conductivity is 55 to 62% IACS; the tensile strength is 550 to 700 MPa; no cracks occur at 180 adhesion bending; and the stress relaxation rate at heating at 150C for 1,000 hr is 30%.