PURPOSE: To obtain an inexpensive polyester desirable for thermally bonding e.g. a nonwoven fabric by copolymerizing a specified amount of glutaric acid and a specified amount of diethylene glycol with a polyethylene terephthalate.

CONSTITUTION: A mixture comprising 65-95 mol.% terephthalic acid, 0-5 mol.% isophthalic acid, 5-35 mol.% glutaric acid, 75-95 mol.% ethylene glycol and 5-25 mol.% diethylene glycol is polymerized to obtain the objective polymer represented by formula I [wherein R is p-phenylene, -(CH2)3- or m-phenylene; and G is a group represented by formula II or III] and having a melting point of desirably 160-220°C.