It is intended to provide a biodegradable polyester resin composition which is excellent in gas barrier properties, mechanical strength and heat resistance and has Theological characteristics advantageously usable in molding a foamed article, etc., a process for producing the same, and a foamed article and a molded article using the same. The biodegradable polyester resin composition contains 100 parts by mass of a biodegradable polyester resin containing 59% mole or more of a hydroxycarboxylic acid unit, 0.01 to 10 parts by mass of a (meth)acrylic acid ester compound and 0.05 to 20 parts by mass of a layered silicate.