The leather-like sheet substrate of the invention comprises a nonwoven fabric of three-dimensionally entangled superfine fibers (A) of at most 0.5 dtex in fineness and a polymer elastomer (B) filled in the entangled interspaces of the nonwoven fabric, in which the superfine fibers (A) comprise an organophosphorus component-copolymerized polyester and the polymer elastomer (B) contains a metal hydroxide or is copolymerized with an organophosphorus component. The leather-like sheet substrate of the invention and artificial leather obtained from it contain no halogen and are resistant to flames. These have a soft feel and are suitable to applications in the interior field that requires flame retardancy, especially to seats for vehicles, etc.