The invention discloses a reinforcing apparatus for a core-drilled building or road. The reinforcing apparatus is cooperatively used with a drilling machine and comprises an apparatus body and a threading cutter head, wherein the apparatus body comprises an installation body and a core drilling body which are coaxially arranged, the core drilling body is uniformly provided with core drilling teeth, and the threading cutter head is telescopically arranged at the side surface of the core drilling body through a telescopic feeding mechanism. The invention also discloses a reinforcing method using the reinforcing apparatus for the core-drilled building or road. The reinforcing apparatus carries out threading on a smooth hole wall after core drilling, which facilitates subsequent reinforcing, enables a repaired road to be firmer and be integrated with an original road under reinforcing and improves firmness of the road. With the reinforcing method, integrated reinforcing of the core-drilled road is realized and the reinforced road has consistent strength with the original road; and the method is easy and convenient to operate.