Polyester resin and method for producing blow-molded product made of polyester resin

A method for producing polyester resin containing an ethylene terephthalate structural unit of not less than 85 mol %, the method comprising:

• a melt-polymerization step of continuously performing melt-polymerization by using an aluminium compound and a phosphorus compound as a polymerization catalyst in two or more polymerization vessels including a final polymerization vessel;
• and
• a solid phase polymerization step of performing solid phase polymerization after the melt-polymerization step,
• wherein the melt-polymerization step includes a final melt-polymerization step performed in the final polymerization vessel, and the final melt-polymerization step satisfies a condition represented by formula (I):
• 410≤T*RT*(P/Al)≤580 (I),
• wherein T represents a temperature (° C.) in the final melt-polymerization step, RT represents residence time (hour) in the final melt-polymerization step, and P/Al represents a molar ratio of phosphorus element to aluminium element in the polyester resin.