To obtain a polyester fiber-based multiple woven/knitted fabric suitable to a fabric for vehicle internal trimming by reducing the amount of a flame-retardant polyester fiber to be used and blending it with a general polyester fiber.

The polyester fiber-based multiple woven/knitted fabric is such that face yarn weave stitches constituting the front face thereof through being separately woven/knitted to the front and back faces thereof and under yarn weave stitches constituting the back face are joined together via medium yarns. In this woven/knitted fabric, flame-retardant polyester fibers with an LOI value of 26 or greater are used as the medium yarn, and flammable ordinary polyester fibers with an LOI value of 21 or less are used as at least either one of the face yarn and the under yarn, and the flame-retardant medium yarn consisting of the flame-retardant polyester fibers accounts for 15 wt.% of the whole multiple woven/knitted fabric. Further, the single filament fineness of the face yarn, the under yarn, and the medium yarn are 8 dtex, respectively, and the total fineness thereof 80-650 dtex, respectively. The total mass of this multiple woven/knitted fabric is 250-800 g/m2, and the mass of flame-retardant polyester fibers account for 15-60 wt.% of the whole multiple woven/knitted fabric.