The copper alloy includes: 17-34 mass% of Zn； 0.02-2.0 mass% of Sn； 1.5-5 mass% of Ni； and the balance Cu and inevitable impurities. The composition of the copper alloy satisfies 12f1=[Zn]+5×[Sn]-2×[Ni]30, 10[Zn]-0.3×[Sn]-2×[Ni]28, 10f3={f1×(32-f1)×[Ni]}1/233, 1.20.7×[Ni]+[Sn]4, and 1.4[Ni]/[Sn]90. The electric conductivity of the copper alloy is 13-25 %IACS or less. The area ratio of an α phase matrix is 99.5 % or more. Alternatively, the copper alloy satisfies 02×(γ)+(β) 0.7, (γ) being the area ratio (%) of a γ phase and (β) being the area ratio (%) of a β phase in the α phase matrix.本發明提供一種銅合金。本發明的銅合金含有17~34mass%的Zn、0.02~2.0mass%的Sn及1.5~5mass%的Ni，剩餘部份包含Cu及不可避免雜質，並且具有12f1=〔Zn〕+5×〔Sn〕-2×〔Ni〕30、10〔Zn〕-0.3×〔Sn〕-2×〔Ni〕28、10f3={f1×(32-f1)×〔Ni〕}1/233、1.20.7×〔Ni〕+〔Sn〕4、1.4〔Ni〕/〔Sn〕90的關係，導電率為13~25%IACS以下，α相所佔之比例以面積率計為99.5%以上，或者，α相基體的γ相的面積率(γ)%與β相的面積率(β)%之間具有02×(γ)+(β)0.7的關係。
