PURPOSE: To make it easy to repair a concrete structure by sticking to a deteriorated concrete wall surface a fiber reinforced plastic plate so formed as to have an irregular surface, and injecting an inorganic material between the wall surface and the plastic plate so as to integrate the wall surface and the plastic plate together.

CONSTITUTION: An inorganic material is injected between a surface to be repaired and a fiber plastic plate so that the surface to be repaired and the fiber plastic plate are integrated together, i.e., fiber reinforced plastic is formed from unsaturated polyester resin into a plate by pulling molding method with glass fiber serving as reinforcing material. Quartz sand No.3 is stuck to one side of the plate by means of epoxy resin adhesion so that the surface of the plate is irregular. The irregular surface is joined to the surface to be repaired normal Portland cement, river sand and concrete having a predetermined amount of river sand mixed therein are placed between the irregular surface and the surface to be repaired and are cured for about twenty-eight days and both of the surfaces are integrated with the concrete. Repairing work can thus be carried out in a short construction period without requiring special techniques for construction.