Copper-clad laminate, wiring board, and copper foil provided with resin

A copper foil with resin, comprising a resin layer and a copper foil in contact with at least one surface of the resin layer,

• wherein the copper foil having a layer treated with a silane coupling agent having an amino group in the molecule as a silane coupling agent layer,
• the resin layer contains a resin composition containing a modified polyphenylene ether compound of which a terminal is modified with a substituent having a carbon-carbon unsaturated double bond or a semi-cured product of the resin composition,
• a chromium element amount on an exposed surface, on which the resin layer is exposed after the copper foil with resin in which the resin layer has been cured is etched with a copper chloride solution, measured by X-ray photoelectron spectroscopy is 7.5 at % or less with respect to a total element amount measured by X-ray photoelectron spectroscopy, and
• a surface roughness of the exposed surface is 2.0 μm or less in terms of ten-point average roughness, and
• wherein the thickness of the silane coupling agent layer is sufficient to cause a nitrogen element that can be confirmed by X-ray photoelectron spectroscopy to exist on the exposed surface upon etching treatment of the copper foil with resin and exposure of the resin layer.