A double composite girder for a bridge, the girder having a rectangular container-like steel box adapted to have concrete filled in an interior thereof, a bottom flange located under the steel box in a longitudinal direction of the steel box, and a web located between the steel box and the bottom flange to connect the steel box and the bottom flange to each other, wherein a top of the web corresponds to an underside of the steel box and an underside of the web is located longitudinally on the center of top of the bottom flange, the double composite girder comprising: a middle span formed between two adjacent piers or between an abutment and a pier; and support spans formed on points of the piers or abutments in such a manner as to be connected to the middle span, wherein the steel box comprises top flanges and located on tops of left and right sides thereof in the longitudinal direction thereof and a U-shaped box located on the undersides of the top flanges and and having an arch-shaped bottom located on the bottom thereof in such a manner as to be adjacent to the top flanges and as the U-shaped box goes toward the middle span from each support span and arch-shaped sides and located on the left and right sides of the arch-shaped bottom to connect the arch-shaped bottom to the top flanges and; the middle span is divided into a first concrete filling section in which the concrete is filled from the arch-shaped bottom to the top flanges and and a second concrete filling section in which the concrete is filled to a given height from the arch-shaped bottom, the first concrete filling section and the second concrete filling section of the middle span being partitioned by a blocking plate, the middle span and each support span being partitioned by an internal finishing plate located to a given height on an area where the concrete in the second concrete filling section and each support span meet each other; a web finishing plate is located vertically on the end of the second concrete filling section to connect the end of the arch-shaped bottom and the bottom flange, a support span top plate is located on top of each support span in such a manner as to be connected to the top flanges and, support span sides and are located on the left and right sides of each support span in such a manner as to be connected to the arch-shaped sides and, and the bottom flange is located on the bottom of each support span in such a manner as to be connected to the web finishing plate; and support span finishing plates or diaphragms are located on both side end portions of the steel box in the longitudinal direction of the steel box in such a manner as to be connected to the support span sides and, so that support span space is formed in each support span and a height of the concrete filled in the support span space corresponds to a height of the internal finishing plate located inside each support span finishing plate. a middle span formed between two adjacent piers or between an abutment and a pier; and support spans formed on points of the piers or abutments in such a manner as to be connected to the middle span, wherein the steel box comprises top flanges and located on tops of left and right sides thereof in the longitudinal direction thereof and a U-shaped box located on the undersides of the top flanges and and having an arch-shaped bottom located on the bottom thereof in such a manner as to be adjacent to the top flanges and as the U-shaped box goes toward the middle span from each support span and arch-shaped sides and located on the left and right sides of the arch-shaped bottom to connect the arch-shaped bottom to the top flanges and; the middle span is divided into a first concrete filling section in which the concrete is filled from the arch-shaped bottom to the top flanges and and a second concrete filling section in which the concrete is filled to a given height from the arch-shaped bottom, the first concrete filling section and the second concrete filling section of the middle span being partitioned by a blocking plate, the middle span and each support span being partitioned by an internal finishing plate located to a given height on an area where the concrete in the second concrete filling section and each support span meet each other; a web finishing plate is located vertically on the end of the second concrete filling section to connect the end of the arch-shaped bottom and the bottom flange, a support span top plate is located on top of each support span in such a manner as to be connected to the top flanges and, support span sides and are located on the left and right sides of each support span in such a manner as to be connected to the arch-shaped sides and, and the bottom flange is located on the bottom of each support span in such a manner as to be connected to the web finishing plate; and support span finishing plates or diaphragms are located on both side end portions of the steel box in the longitudinal direction of the steel box in such a manner as to be connected to the support span sides and, so that support span space is formed in each support span and a height of the concrete filled in the support span space corresponds to a height of the internal finishing plate located inside each support span finishing plate.