A penetration reinforcing agent for preventing aging of concrete is prepared by using an inorganic silicate compound having an ethoxy or methoxy group and a monomer having a hydroxyl (OH) group. When the penetration reinforcing agent is applied onto the surface of a concrete structure it penetrates the concrete structure where it is hydrolyzed by water existing within the concrete to form silica (SiO2) having a particle size of several nanometers, is gelled by a sol-gel process and reacts with concrete hydrates, so that internal pores of the concrete structure are compactly filled with the reaction products. The penetration reinforcing agent is effective in enhancing the strength of, inhibiting penetration of aging factors into, improving waterproofness of, and preventing neutralization of the concrete structure.