A copper based alloy for use as a material for electrical and electronic parts, which is excellent in electric conductivity, solder-exfoliation resistance when bent, high-temperature creep strength, and migration resistance, as well as in hot workability and blankability, consisting essentially, by weight percent, of 1.3 to 2.7% Ni, 0.2 to 0.79% Sn, 0.2 to 0.8% Si, 0.4 to 2.0% Zn, 0.01 to 0.12% Fe, 0.002 to 0.10% P, 0.001 to 0.10% Mg, 0.0002 to 0.0008% C, more than 0.01% and up to 0.2% at least one element selected from the group consisting of Cr and Zr, and the balance being Cu and inevitable impurities.