PURPOSE: A composition, obtained by blending a mixed polyamide of nylon 66 and nylon 6 with a triazine based flame retardant and specific zinc salt, and useful as engineering plastics having improved flame retardancy, heat resistance and melt fluidity.

CONSTITUTION: A composition obtained by blending (A) a mixed polyamide consisting of 70W99wt% polyamide consisting essentially of hexamethylene adipate and 30W1wt% polyamide consisting essentially of -caprolactam with (B) a triazine based flame retardant and (C) a salt of zinc with a carboxylic acid, phosphoric acid, thiazole or dithiocarbamate. The amounts of the respective components based on 100pts.wt. component (A) are 0.1W30pts.wt., preferably 0.5W20pts.wt. component (B) and 0.05W20pts.wt., preferably 0.1W5pts.wt. component (C).