To provide a Cu-Ni-Si based copper alloy that has an excellent strength and electrical conductivity, and an excellent die wear resistance and press punchability.SOLUTION: Provided is a Cu-Ni-Si based copper alloy, containing, in mass%, Ni: 3.0 to 5.0%, Si: 0.5 to 1.5%, the balance consisting of Cu and inevitable impurities, 0.2% yield stress YS in the rolling parallel direction is 950 to 1300 MPa, elongation EL in the rolling right-angle direction is 3% or less, conductivity is 25% IACS or more, and (0.2% yield strength YS in the rolling parallel direction)/(elongation EL in the rolling right-angle direction) is 317 to 1300 (MPa/%), and furthermore, the spring deflection limit value in the rolling right-angle direction is 850 MPa or more.SELECTED DRAWING: Figure 1
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