To obtain a polymer composition having high flame-retardant characteristic without using a halogenated flame retardant and excellent in moldability by making the composition include a specific polymer and a flameproofing amount of a melamine compound.

This polymer composition comprises (A) 100 pts.wt. polymer composed of carbon monoxide and one or more kinds of olefins and (B) preferably 5-50 pts.wt. melamine compound containing (mono)melamine phosphate. Furthermore, the polymer is preferably a terpolymer comprising carbon monoxide, ethylene and propylene. The polymer composition preferably further contains other flame retardant such as phosphonate, phosphate, an alkaline earth metal carbonate, alkaline earth metal hydroxide, a metal borate or PTFE.