The present invention relates to a method of producing a substrate, including the steps of preparing a substrate having a nickel layer formed on a copper layer through plating, subjecting the nickel layer to thermal treatment at 800-1000° C., and epitaxial-growing an intermediate layer on the nickel layer, after the step of subjecting the nickel layer to thermal treatment. According to the present invention, there can be provided a substrate that allows the orientation and flatness at the surface of a nickel layer to be improved, and a method of producing the substrate.