We report the changes in out-of-plane vibration characteristics due to the seismic retrofit of historic masonry buildings based on the result of microtremor measurement. Major findings from the research are as follows; (1) Natural frequencies increase nearly 1.1 to 1.9 times by reinforcement. And, the increasing rate of natural frequency becomes smaller as it becomes high order. (2) Using steel frame for reinforcement, out-of-plane deformation of masonry wall is restrained. And, using shear wall, it is restrained greatly. (3) 1<sup>st</sup> damping factor doesn't change remarkable by reinforcement.