A copper alloy sheet strip with a surface coating layer, comprising: a copper alloy sheet strip, as a base material, consisting of Ni: 0.4 to 2.5% by mass, Sn: 0.4 to 2.5% by mass, and P: 0.027 to 0.15% by mass, a mass ratio Ni/P between the Ni content to the P content being less than 25, as well as one or more of Fe: 0.0005 to 0.15% by mass, Zn: 1% by mass or less, Mn: 0.1% by mass or less, Si: 0.1% by mass or less, Mg: 0.3% by mass or less, and optionally one or more of Cr, Co, Ag, In, Be, Al, Ti, V, Zr, Mo, Hf, Ta and B in the total amount of 0.1% by mass or less, with the balance being Cu and inevitable impurities, and having a structure in which precipitates of a Ni-P intermetallic compound are dispersed in a copper alloy matrix, each precipitate having a diameter of 60 nm or less, 20 or more precipitates each having a diameter of 5 nm or more and 60 nm or less being observed in the visual field of 500 nm × 500 nm; and the surface coating layer composed of a Ni layer, a Cu-Sn alloy layer and a Sn layer formed on a surface of the copper alloy sheet strip in this order; wherein the Ni layer has an average thickness of 0.1 to 3.0 μm, the Cu-Sn alloy layer has an average thickness of 0.1 to 3.0 μm, and the Sn layer has an average thickness of 0.05 to 5.0 μm; wherein the Cu-Sn alloy layer is partially exposed on the outermost surface of the surface coating layer and a surface exposed area ratio thereof is in a range of 3 to 75%; and wherein the Cu-Sn alloy layer is composed of a ε phase and a η phase, the ε phase existing between the Ni layer and the η phase, a ratio of the average thickness of the ε phase to the average thickness of the Cu-Sn alloy layer being 30% or less, and a ratio of the length of the ε phase to the length of the Ni layer being 50% or less. a copper alloy sheet strip, as a base material, consisting of Ni: 0.4 to 2.5% by mass, Sn: 0.4 to 2.5% by mass, and P: 0.027 to 0.15% by mass, a mass ratio Ni/P between the Ni content to the P content being less than 25, as well as one or more of Fe: 0.0005 to 0.15% by mass, Zn: 1% by mass or less, Mn: 0.1% by mass or less, Si: 0.1% by mass or less, Mg: 0.3% by mass or less, and optionally one or more of Cr, Co, Ag, In, Be, Al, Ti, V, Zr, Mo, Hf, Ta and B in the total amount of 0.1% by mass or less, with the balance being Cu and inevitable impurities, and having a structure in which precipitates of a Ni-P intermetallic compound are dispersed in a copper alloy matrix, each precipitate having a diameter of 60 nm or less, 20 or more precipitates each having a diameter of 5 nm or more and 60 nm or less being observed in the visual field of 500 nm × 500 nm; and the surface coating layer composed of a Ni layer, a Cu-Sn alloy layer and a Sn layer formed on a surface of the copper alloy sheet strip in this order; wherein the Ni layer has an average thickness of 0.1 to 3.0 μm, the Cu-Sn alloy layer has an average thickness of 0.1 to 3.0 μm, and the Sn layer has an average thickness of 0.05 to 5.0 μm; wherein the Cu-Sn alloy layer is partially exposed on the outermost surface of the surface coating layer and a surface exposed area ratio thereof is in a range of 3 to 75%; and wherein the Cu-Sn alloy layer is composed of a ε phase and a η phase, the ε phase existing between the Ni layer and the η phase, a ratio of the average thickness of the ε phase to the average thickness of the Cu-Sn alloy layer being 30% or less, and a ratio of the length of the ε phase to the length of the Ni layer being 50% or less.