Method for producing polyester

A method for producing a polyester, comprising:

• culturing a microorganism having a polyester-producing capability in a culture solution comprising a carbon source and a nitrogen source, the polyester comprising at least a 3-hydroxybutyrate unit as a polymerization unit, wherein the produced polyester has a weight average molecular weight of 1,000,000 or greater determined by gel permeation chromatography calibrated with polystyrene standards and comprises at least the 3-hydroxybutyrate unit as the polymerization unit, and wherein the culture solution has a pH of 4 to 7.5, the culture is a batch culture, and the culture satisfies conditions (a) and (b) below:
• (a) an osmotic pressure of the culture solution at the initiation of the culture is from 200 mOsm to 900 mOsm;
• and
• (b) a nitrogen atom concentration of the culture solution at the initiation of the culture is 0.30 g/L or greater.