To provide a resin composition comprising thermosetting resins having a benzoxadine ring and excellent in compatibility with liquid rubber.

The resin composition comprises a thermosetting resin (I) having a benzoxadine ring structure expressed by general formula (1) in the main chain and a thermosetting resin (II) having a benzoxadine ring structure expressed by general formula (2) in the main chain. In general formulae (1) and (2), Ar1 and Ar2 are each independently a tetravalent aromatic group which is a difunctional phenol residue; R1 is an aromatic organic group which is a 6-30C aromatic diamine residue; R2 is an aliphatic organic group which is a 1-20C aromatic diamine residue.