Abstract: A flame-retardant polymer composition comprising a flame-retardant polymer and a different kind of a polymer, the amount incorporated of the flame-retardant polymer being 2 to 50 percent by weight based on the different polymer and said flame-retardant polymer being prepared by copolymerizing 2 to 100 percent by weight of a monomer represented by the following general formula (A) ##SPC1##wherein R.sup.1 and R.sup.2 stand for H or CH.sub.3, R.sup.3 is a linear or branched alkylene group having 2 to 6 carbon atoms, which may be substituted by a hydroxyl group, X designates Br or Cl, n is a number of from 3 to 5, and m is a number of from 0 to 1,With 98 to 0 percent by weight of at least one unsaturated compound copolymerizable with the monomer (A).