To obtain the subject readily producible and transparent material comprising a cyclic phosphonic ester represented by a specific formula, excellent in flameproof and useful in the electronic and electrical industrial fields.

This material comprises at least one cyclic phosphonic ester represented by formulas I and/or II (R1 to R3 are each a 1-12C alkyl, aryl or alkylaryl) in an amount of 5-60 pts.wt. based on 100 pts.wt. epoxy resin molding material. Furthermore, the material preferably contains phosphorus in an amount of 1-10wt.% based on the total weight of the material, at least another flameproofing agent and especially a compound containing bromine, concretely tetrabrominated bisphenol A.