Abstract: Disclosed herein is a bracket structure for increasing strength of a concrete structure and enabling easy construction. The bracket structure includes an affixing bracket and a pre-stressing steel plate. The affixing bracket comprises a holding member connected to a bottom of the concrete structure using an anchor bolt, and a support member connected to the holding member and forming a channel to increase the moment of inertia of area of the concrete structure. The pre-stressing steel plate is connected to the support member of the affixing bracket, and applies stress to the concrete structure.