This invention relate to a copper-clad laminate with good adhesion between a copper foil and a layer of polyimide resin useful for high-density printed wiring boards. The copper-clad laminate having a copper foil treated with a heterocyclic compound containing nitrogen and sulfur as an organic surface treating agent and a layer of polyimide resin satisfying either of the following requirements: the concentration of sulfur atoms derived from the organic surface treating agent in the interface of copper and polyimide is in the range of 0.01-0.24 wt % as determined by an Energy dispersive X-ray spectroscopy (EDX); the weight of sulfur atoms derived from the organic surface treating agent per unit area of the copper foil is in the range of 2.5-3.1 mg/m<SUP>2</SUP>; and the concentration of sulfur atoms derived from the organic surface treating agent existing in the range from the surface to a depth of 16 nm of the copper foil is in the range of 1.73-2.30 atom % as determined by X-ray photoelectron spectroscopy (XPS).
