A thermosetting resin composition comprising (A) a thermoplastic resin having a structure represented by the following general formula (a) and/or a structure represented by the following general formula (b) in which 5 to 99 mol % of hydroxyl groups of polyhydroxyether are esterified, and (B) a thermosetting resin: wherein R1 represents C1-18 aliphatic or aromatic-ring-containing alkylene group or —SO2—, 5 to 99 mol % of R2 represent a straight chain or cyclic carbonyl group or aromatic carbonyl group having 1 to 20 carbon atoms, the residue 95 to 1 mol % represent a hydrogen atom, and R3 represents a hydrogen atom or a methyl group, with a proviso that a plurality of R3's may be the same or different.