A Cu—Ni—Si based copper alloy, comprising 1.2 to 4.5% by mass of Ni, 0.25 to 1.0% by mass of Si and the the balance Cu with inevitable impurities, wherein when an X-ray diffraction intensity of a {111} plane of a rolled surface and that of a {111} plane of a pure copper powder standard specimen is represented by I{111}, I0{111} respectively, I{111}/I0{111} is 0.15 or more, wherein when an X-ray diffraction intensity of a {200} plane of the rolled surface and that of a plane {200} of the pure copper powder standard specimen is represented by I{200}, I0{200} respectively, I{200}/I0{200} is 0.5 or less, when an X-ray diffraction intensity of a {220} plane and a plane {311} of the rolled surface is represented by I{220}, I{311} respectively, I{111}/(I{111}+I{200}+I{220}+I{311}) is 0.2 or more, a bending coefficient is 130 GPa or more, a yield strength YS satisfies: YS=>−22×(Ni mass %)2+215×(Ni mass %)+422, and the electrical conductivity is 30% IACS or more both in a direction transverse to ro
