To provide a method for manufacturing a circuit substrate including a cured film of a photosensitive resin composition which can be microfabricated owing to its photosensitivity, can be developed with a diluted alkaline water solution, can be cured at a low temperature, is very flexible, is excellent in electrical insulation reliability, soldering heat resistance, resistance to an organic solvent, and property of adhesion with a sealant, and in which the warpage of a substrate after curing is small.

The problems can be coped with by using the method for manufacturing a circuit substrate in which the cured film of the photosensitive resin composition is formed on a substrate at least by (1) a step in which a film is formed on a substrate using a photosensitive resin composition, (2) an exposure step, (3) an alkaline developing step, (4) an ionic impurity cleaning and removing step, and (5) a thermal curing step, wherein the photosensitive resin composition includes at least (A) an imidized tetracarboxylic acid, (B) a diamino compound and/or isocyanate compound, (C) a photosensitive resin, and (D) photopolymerization initiator.