In Japan, it is important to be able to determine the factors affecting changes in the vibration characteristics of wooden buildings resulting from their seismic strengthening, so as to ensure their seismic resilience. This study set out to determine the effect of seismic strengthening on the vibration characteristics of a wooden building and to clarify the factors affecting the changes in the vibration characteristics based on micro-tremor measurements. The results of the micro-tremor measurements were compared with the results of a seismic diagnosis. The main findings were as follows; 1) The installation of seismic strengthening increases the natural frequency. 2) The amplitude of the structure plane in which the steel columns and structural plywood were installed was reduced. 3) The results of micro-tremor measurements and a seismic diagnosis exhibited the same tendency regarding the effects of seismic strengthening.