Abstract: There is disclosed a method for producing a substrate for single crystal diamond growth, comprising at least a step of preliminarily subjecting a substrate before single crystal diamond growth to a bias treatment for forming a diamond nucleus thereon by a direct-current discharge in which an electrode in a substrate side is a cathode, and wherein in the treatment, at least, a temperature of the substrate from 40 sec after an initiation of the bias treatment to an end of the bias treatment is held in a range of 800° C.±60° C. There can be provided a method for producing a substrate for single crystal diamond growth, by which a single crystal diamond can be grown more certainly.