To provide an electrolytic copper alloy foil that has a low profile and large mechanical strength in a normal state, and hardly deteriorates with heat even heated at 300°C or higher.

The electrolytic copper alloy foil contains tungsten, and the remnants are constituted by copper (including impurities mixing inevitably). The electrolytic copper alloy foil also includes tungsten, carbon, sulfur, nitrogen, and chlorine, and the remnants are constituted by copper (including the impurities mixing inevitably). To a sulfuric acid-copper sulfate electrolytic solution, thiourea series compound, tungsten salt, and chloride ion are added to be subjected to electrolytic deposition, thereby producing the electrolytic copper alloy foil.