The present invention relates to biodegradable plastics and biodegradable plastic products thereof having flexibility, and more specifically, it aims to provide a plasticizer for providing aliphatic polyester, in particular, polylactic acid with flexibility, an aliphatic polyester composition using the same, a film, a sheet, a bag and the like obtained by molding said composition, that are, with respect to 100 parts by weight of aliphatic polyester, (1) an aliphatic polyester compound which contains polyglycerol acetic ester by 5-50 parts by weight, (2) an aliphatic polyester compound which contains polyglycerol acetic ester and acetic and fatty acid ester of glycerol having a specific structure by 5-50 parts by weight, and (3) flexible products which are obtained by molding the fatty polyester compound indicated in the above (1) or (2) into films, sheets, bags or the like.
