Molecular weight distribution and mean square radius as a function of molecular weight for biodegradable aliphatic polyesters have been measured by multiangle laser light scattering (MALLS) detector for size exclusion chromatography (s.e.c.). The difference of their molecular structures is discussed in relation to the melt elasticity, which contributes to processability for extrusion coating and extrusion foaming. The evaluated values of branching ratio indicate the existence of long chain branched structures.