To obtain a polyester fiber which has excellent color tone (b value), uniform and continuous micropores, excellent water absorption properties, hygroscopicity, yet a very small amount of deposit occurring on a nozzle even in continuous spinning through a spinneret for long hours and excellent formability, and to provide a method for producing the same.

A catalyst containing a specific titanium compound and a phosphorus compound for producing a polyester, is used. At an arbitrary stage before the completion of the synthesis of the polyester, a specified organic sulfonic acid metal salt is added to the polyester. The obtained polyester composition is made into a fiber and treated with an aqueous solution of an alkali compound and at least a part of the organic sulfonic acid metal salt is removed to form micropores on the cross section of the fiber.