PURPOSE: To efficiently produce a polyester amide excellent in mechanical strength at ambient and high temperatures, molding processability, chemical resistance and transparency.

CONSTITUTION: This method for producing a polyester amide is to dissolve 25-250 pts.wt. polyamide having 1.8-7.0 reduced viscosity (in a 1g/dL98% sulfuric acid solution at 20°C) in 100 pts.wt. polyester constituent component composed of an aliphatic dicarboxylic acid consisting essentially of adipic acid and an aliphatic diol consisting essentially of at least one selected from the group consisting of butylene glycol and neopentyl glycol, esterify the polyester constituent component at 150-230°C and then polymerize the resultant transparent and homogeneous solution at 200-260°C under a vacuum.