A copper-based alloy wire made of a material selected from the group consisting of a copper-gold alloy, a copper-palladium alloy and a copper-gold-palladium alloy is provided. The alloy wire has a polycrystalline structure of a face-centered cubic lattice and consists of a plurality of equi-axial grains. The quantity of grains having annealing twins is 10 percent or more of the total quantity of the grains of the copper-based alloy wire.