A system and method of repairing or reinforcing an existing structure using a reaction force of pressurizing means are provided. In a state in which structure supporting means, such as a steel pile, is pressed fit into the ground located under an existing structure to reach a predetermined rigid bearing layer, and the existing structure is lifted by the structure supporting means, a target portion for repair or reinforcement can be repaired or reinforced, irrespective of the construction site or space, without causing any harmful environmental impact.