A blending of a styrenic resin, and a flame retardant comprising a phenolic resin and a phosphazene compound to a polyalkylene arylate-series resin imparts flame retardancy to a polyalkylene arylate-series resin. The phosphazene compound is a cyclic phenoxyphosphazene compound, a linear phenoxyphosphazene compound, or a crosslinked phenoxyphosphazene compound. The obtained polyalkylene arylate-series resin composition has excellent heat resistance and high flame-retardancy without bleeding out the flame retardant.