Recently, there have been a large number of remodeling (or renovation) works in old buildings in urban areas. Compared to new buildings, environmental risk might be more significant in such buildings where remodeling works are going on, since some parts of the building may still be in service for people. This study was carried out to investigate the impacts of remodeling works on the indoor air quality (IAQ) of a large building (a 22 stories university library). Indoor air monitoring was conducted during and after the remodeling works every two weeks for a one year period, and target compounds included BTEX, styrene, TVOC, carbonyl compounds such as formaldehyde and acetaldehyde. $CO,;CO_2,;PM_{10}$, and $PM_{2.5}$. Overall, the IAQ appeared to be recovered within two months after the remodeling works. However, in some places, concentrations of formaldehyde, toluene, xylene. and ethylbenzene showed higher levels even after works than those during the works. The results indicate that painting, glues and office furnitures are major sources of aromatic VOCs and formaldehyde. Therefore, in order to decrease the concentrations of toxic VOCs, the use of environmental-friendly building materials is strongly recommended during the remodeling works. In addition, IAQ control and management scheme (for example, baking the inside of the building) should be taken into consideration before reopening the buildings.