Abstract: The present invention provides a circuit substrate and a circuit-formed suspension substrate comprising the circuit substrate, the circuit substrate comprising a metal foil substrate and an insulating layer composed of a polyimide resin formed on the metal foil substrate, wherein the polyimide resin is one obtained by the reaction of (A) p-phenylene diamine and (B) acid anhydrides of (a) 3,4,3′,4′-biphenyltetracarboxylic acid dianhydride and (b) 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane. Since a coefficient of linear thermal expansion of the polyimide resin is close to that of various metal foils, the circuit substrate causes no cracking on the resin layer and scarcely causes warpage, and the resin layer does not separate.