A halogen-free and flame-resistant photosensitive resin composition is provided, which has properties necessary for a solder resist (insulative property, solder heat resistance, alkali developability and the like) and is capable of forming a film that is excellent in folding endurance even after an IR reflow process. A flexible circuit board employing the photosensitive resin composition and a circuit board production method are also provided. The photosensitive resin composition comprises: (A) a linear polymer of an ethylenically unsaturated compound comprising a carboxyl-containing ethylenically unsaturated compound; (B) an epoxy resin; (C) a polymerizable compound containing an ethylenically unsaturated group; (D) a photopolymerization initiator; and a cyclic phosphazene (E) represented by the following general formula (1):