A substrate for a printed wiring board, the substrate includes a base film containing polyimide as a main component and a sinter layer disposed on at least a portion of a surface of the base film and containing copper nanoparticles. The base film contains a nitrogen atom bonded to a copper atom of the copper nanoparticles, an average number of the nitrogen atom bonded to the copper atom per unit area of the surface of the base film on which the sinter layer is disposed is 2.6×1018 atoms/m2 to 7.7×1018 atoms/m2, and the average number is an average number calculated for a measurement region estimated to have a thickness of 3 nm from a measurement value of the surface of the base film measured by X-ray photoelectron spectroscopy.