(EN) A purpose of the present invention is to provide an electrolytic copper foil which is superior in physical properties after high-temperature heating to conventional electrolytic copper foils and which is suitable also as the negative-electrode current collector of a lithium-ion secondary battery. The electrolytic copper foil is characterized by having an original-state tensile strength of 600 MPa or higher and a tensile strength after 350ºC×1 hour heating of 470 MPa or higher. Also provided is a process for producing the electrolytic copper foil, characterized by using an electrolytic copper solution acidified with sulfuric acid, the solution containing polyethyleneimine with a molecular weight of 10,000-70,000 in a concentration of 20-100 mg/L and having a chlorine concentration of 0.5-2.5 mg/L.
