The utility model discloses a reinforcing device for a T-shaped beam and a beam case. The reinforcing device comprises a steel plate fastened by an anchor bolt and wrapped outside a part to be reinforced, one end of the anchor bolt is embedded into the part to be reinforced, and the other end of the anchor bolt penetrates through the steel plate; and concrete is poured between the steel plate and the part to be reinforced, a reinforcing steel bar mesh is embedded in the concrete, and the reinforcing steel bar mesh is hung on the anchor bolt. The reinforcing device adopts the steel plate which is fastened by the anchor bolt and wrapped outside the part to be reinforced, one end of the anchor bolt is embedded into the original structure, and the other end of the anchor bolt penetrates through the steel plate wrapped outside the part to be reinforced, and after screw caps on the outer side are screwed down in multiple times, the reinforcing device is welded and fixed. In construction, help of other components is not needed for reinforcing the steel plate, meanwhile integrity among new concrete, old concrete and the steel plate wrapped outside the part to be reinforced can be promoted, and sliding resistance among the new concrete, the old concrete and the steel plate wrapped outside the part to be reinforced is enhanced.