A star-branched polyester polyol is obtained by polymerizing lactide or lactic acid, using, as an initiator, a fat and oil composed mainly of a triacylglycerol that has at least three hydroxyl groups or epoxy groups in its molecule. This polyester polyol has low crystallinity and a low melting point, and thus shows good working properties when used in various applications. Furthermore, this polyester polyol is derived from renewable resources, and, thus, it is highly desirable in view of its effectiveness in protecting the global environment and preventing fossil resources from being depleted.