To provide a sheet-shaped cast ingot of a copper alloy in which dispenses with hot rolling treatment while attaining simplification, reduction of cost or the like in a production process and further obtaining higher strength; to provide a method for producing a copper alloy strip; and to provide a production device for a cast ingot of a copper alloy.

Molten metal 1 is continuously teemed into a mold 15 in which the distance between the center of the hollow part and the inner wall (equivalent to the length of the short side in the cross-section of the hollow part/2) is ≤20 mm. This is continuously discharged from the inside of the mold 15, and is thereafter cooled by a water-cooled device 16 in such a manner that cooling velocity to 700°C is controlled to ≥10°C/sec, so as to obtain a Cu-Ni-Si based sheet-shaped cast ingot 2 of a copper alloy, and oxide scale is removed. The cast ingot is subjected to cold rolling at a draft of ≥50% for one or more times and age hardening treatment at 300 to 600°C for one or more times, so as to obtain the cast ingot 2, and, without performing heat treatment at a temperature higher than 600°C, a copper alloy strip is obtained.