A readily-adhesive polyester film for optical applications that suppresses rainbow reflections under fluorescent lamps and has excellent adhesion to a hard coating layer and exhibits excellent adhesion at high temperatures and high humidities (resistance to humidity and heat) includes a biaxially-stretched polyester film and a coating layer that is stacked on at least one side of the polyester film and produced by applying to at least one side of the polyester film an aqueous coating liquid containing a resin composition including (A) an aqueous polyester resin and (B) at least one compound that is a water-soluble titanium chelate compound, a water-soluble titanium acylate compound, a water-soluble zirconium chelate compound or a water-soluble zirconium acylate compound as main components. The mixing ratio (A)/(B) is from 10/90 to 95/5 by weight. After that the coating is dried and then stretched in at least one direction.