Abstract: As a fiber for weight reduction, a modified polyester fiber, which is obtained by copolymerizing: ethylene terephthalate as a main constitutional unit; equal to or more than 16 mol % and equal to or less than 25 mol % of an aliphatic dicarboxylic acid having equal to or more than 4 and equal to or less than 8 carbon atoms; and equal to or more than 2 mol % and equal to or less than 5 mol % of a metal sulfonate group-containing aromatic dicarboxylic acid, is used. This modified polyester fiber has a single fiber fineness of equal to or more than 0.6 dtex and equal to or less than 3.5 dtex. A mixed woven or knitted fabric composed of two or more types of fibers, which are the modified polyester fiber, a regular polyester fiber, and optionally, a polyurethane fiber, is capable of exhibiting good etching finish properties by using an etching finish agent that contains an etching finish accelerator, for example, a Mei printer OP-2 (manufactured by Meisei Chemical Works, Ltd.