Reinforcing panel having high durability, high strength, and high hardness is applied such that a concrete structure may be repaired to have excellent resistance to an external environment and to be structurally excellent. In comparison to existing bonding methods, a concrete structure and a reinforcing panel may be completely attached to each other as a whole using a repairing material with high fluidity as a cement-based material injected into a repair cross section. Part with microcracks is completely filled with repairing cement mortar injected at high pressure. Since reinforcing panel is precast-fabricated in a factory, embossing, intaglio, color, and the like may be easily added to an external surface of the reinforcing panel and an excellent exterior may be provided after repair due to an aesthetic cross section thereof The reinforcing panel fabricated in a factory is applied as to reduce labor costs and construction costs.