A surface-treated copper foil includes, on at least one surface of an untreated copper foil, a finely roughened layer formed of copper particles in which primary particles have a particle size of 10 nm to 110 nm or less, and a heat-resistant-treatment layer containing nickel and phosphorus, wherein a treated surface has a surface area ratio of 5.1 or more per 1 m2 of a two-dimensional area, the surface area ratio being calculated from a specific surface area measured by a krypton gas adsorption BET method, and a coating mass of the nickel is 2 mg or more per 1 m2 of a surface area.