PROBLEM TO BE SOLVED: To obtain an aseismatic reinforcing method which sufficiently obtains necessary strength, reduces vibration and noise during drilling work with a drill while constructed, does not emit mal odor and is carried out at a lower cost when carrying out the aseismatic reinforcement of an existing building, and to provide an aseismatic reinforcing method for the existing building excellent in construction efficiency and aseismatic reinforcing effect which improves the seismic force transmitting performance of shrinkage-compensating mortar filled into a gap between an existing skeleton and a reinforcing member to the reinforcing member and reduces the installation number of anchor bolts or limits installation positions to positions where stress is considered to be generated. SOLUTION: The aseismatic reinforcing method for the existing building integrates the reinforcing member with a column-beam frame by arranging it in the column-beam frame of the existing building. The aseismatic reinforcing method includes a step for fixing by arranging a plurality of the anchor bolts at the inner circumference of the column-beam frame, a step for arranging a reinforcing member including an H steal beam having a flange in at least a part of an outer frame, and a step for filling and hardening high-performance hydraulic mortar between the reinforcing member and the column-beam frame. COPYRIGHT: (C)2009,JPO&INPIT