Method for producing polyester

A method for producing polyester, the method comprising:

• mixing, in an organic solvent, a cyclic ester with an alkyl aluminum compound represented by a formula [I]:
• Rn Al X3-n
• wherein, in the formula [I], n represents an integer from 1 to 3, R each independently represents a linear or branched C1-20 alkyl group, and X each independently represents a halogen atom or a hydrogen atom;
• and then
• mixing the resulting mixture with at least one ring-opening polymerization catalyst selected from the group consisting of an organic lithium ring-opening polymerization catalyst, an organic sodium ring-opening polymerization catalyst, an organic potassium ring-opening polymerization catalyst, an organic zinc ring-opening polymerization catalyst, an organic magnesium ring-opening polymerization catalyst, an organic tin ring-opening polymerization catalyst, an organic calcium ring-opening polymerization catalyst, an organic titanium ring-opening polymerization catalyst, and an amine ring-opening polymerization catalyst to allow ring-opening polymerization of the cyclic ester.