Method for producing polymeric molded product comprising pretreatment by heating

A method for producing a polymeric molded product, the method comprising:

• subjecting a crystalline polyhydroxyalkanoate to a heating treatment at a temperature equal to or higher than a glass transition temperature;
• and
• melt-molding a polyhydroxyalkanoate yielded by the heating treatment,
• wherein the polyhydroxyalkanoate comprises lamellar crystals that are different in lamellar thickness, in a temperature range where some of the lamellar crystals undergo melting and flowing, and the other balance lamellar crystals remain unmelted, and
• wherein the temperature range is 109.8° C. to 139.1° C., which is a range which is higher than an outflow onset temperature determined in accordance with a flow tester temperature raising method and lower than an extrapolated melting offset temperature.