To form a circuit with a uniform circuit width, each of etched sides of the circuit having a gradient in a range of 80 to 95 degree, by preventing sag of a copper foil in in-plane directions of the copper foil due to etching, upon forming the circuit by etching the copper foil of a copper-clad laminate plate.

For forming the circuit by etching, a resist layer for etching 3 is formed on a surface of a layer 7 of a metal such as cobalt or nickel, or an alloy, with an etching rate smaller than that of copper, the layer 7 being formed on the etching side one of surfaces of the copper foil 1 for the electronic circuit, and the copper foil 1 with the layer 7 is etched by using a cupric chloride aqueous solution.