Ventilation is essential to maintain a healthy indoor environment. However, in summer and winter, thermal conditions of outdoor air are so poor that ventilation cannot but increase energy consumption. Thus, energy-efficient ventilation system is very important to reduce energy consumption. Thermal labyrinth system is a ventilation system which intakes outdoor air through an underground concrete structure shaped like a labyrinth. By the heat exchange with ground, this system can pre-cool and pre-heat the outdoor air in summer and winter, respectively. The aim of this study is to analyze the energy performance and economical efficiency of thermal labyrinth system, applied to the E University building recently built in Seoul. As results, outdoor air cooling+dehumidification and heating+humidification peak loads were found to be reduced by 47.6% and 41.2%, respectively. Annual outdoor air conditioning energy demand was found to be reduced by 31.3% and payback period was found to be 14.2years.