Condensation in the public underground space of apartment buildings can cause the growth of bacteria and contaminate the internal environment. The purpose of this study is to quantitatively analyze the reduction effect of condensation by applying insulation for the prevention of condensation. In order to analyze the reduction effect of condensation in summer season the surface temperature was predicted by simulation program and verified by monitoring after test construction. In this way the simulated and measured surface temperature results within 5% error rate was almost similar and generation of condensation was calculated to analyze the reduction effect. As a result, the total generation of condensation of floor area by applying 60mm insulation decreased 94.2%, and wall area by applying 20mm insulation decreased 89.9%.