Disclosed are a polyester fiber having excellent antibacterial performance, deodorizing performance, and stain resistance together with sufficient durability; a method for producing the same; a cloth; a textile product; and a polyester formed article. The polyester fiber, cloth, or polyester formed article has a pH of less than 7.0 achieved by subjecting a polyester fiber, a cloth, or a polyester formed article containing a polyester copolymerized with an ester-forming metal sulfonate compound and/or an ester-forming phosphonium sulfonate compound to an acid treatment, or alternatively by applying a processing liquid having a pH of less than 7.0 to a polyester fiber, a cloth, or a polyester formed article.