PURPOSE: To produce a Cu alloy for electrical and electronic apparatus parts excellent in strength and electrical conductivity by subjecting a Cu-Ni-Si alloy having a specified compsn. to solution treatment, heat treatment and cold working under specified temp. conditions.

CONSTITUTION: The continuously cast slab of a Cu-Ni-Si alloy contg., by weight, 4.1 to 10% Ni, 1.0 to 1.5% Si, <0.2% Mn, <1.0% Zn and <15ppm S is held at 950 to 1000°C for ≥1min, is subjected to solution treatment, is subjected to hot rolling at need and is rapidly cooled in the temp. range of 300 to 600°C at ≥10°C/sec cooling rate by water injection. Next, it is subjected to primary heat treatment of executing heating at 450 to 550°C for 1 to 30min after executing cold rolling at ≥50% working ratio and is subjected to cold rolling at 30 to 80% working ratio to form it into a thin sheet shape, thereafter is subjected to secondary heat treatment of executing heating at 380 to 440°C for 5 to 180min and is annealed, or it is moreover subjected to cold rolling at 5 to 15% working ratio and is thereafter annealed at 250 to 350°C. The Cu alloy thin sheet excellent in strength and electrical conductivity for electrical and electronical apparatus parts can be produced.