The purpose of this study is investigating the improvement effects of Indoor Air Quality(IAQ) and Occupants" Perceived Air quality(PAQ) with the indoor plants in university classrooms. First of all, we conduct the measurement survey of IAQ to its original condition in this classrooms. In other words, there is no indoor plants. And then we find out that this classrooms are need of improvement in IAQ. It is especially important to reduce CO<SUB>2</SUB> concentration that was continually increase by respiration of students. So we arranged indoor plants by the windows, and we measured the increasing level of CO<SUB>2</SUB> according to existence of indoor plants. The result of this study is following. The increasing level of CO<SUB>2</SUB> nonexistence IPs was fore times more higher compared to existence of IPs. And PAQ of students actually improve by IPs.