The purpose of this study was to investigate the concentration of aldehydes from new apartments in three cities(Suncheon, Yeosu and Gwangyang) of Chonnam region. The target apartments were within 3 months after the completion of construction. Aldehydes were sampled using 2,4-DNPH cartridge and analyzed by HPLC. Temperature and relative humidity were monitored continuously every one minute by digital temperature and hygrometer. As the concentration ratio of formaldehyde between back-up and front cartridge was 3.94～6.97 %, the 2,4-DNPH cartridge mathod satisfied a breakthrough problem for the sample collection. The repeatability of retention time and peak area for HPLC were excellent as 0.5 % and 1.5 %, respectively. The upper floor of S apartment(16 pyong) showed the highest concentration of formaldehyde as 1,093.1 ㎍/㎥. The average concentration of formaldehyde was the highest in K apartment(52 pyong) as 1,045 ㎍/㎥. The average concentration of formaldehyde in S apartment(16 pyong) and C apartment(25 pyong) were 872.6 ㎍/㎥ and 737.5 ㎍/㎥, respectively. The I/O ratios of formaldehyde were 56.9～60.0(mean : 59.1), 37.9～43.3(mean : 39.8) and 18.3～29.3(mean : 23.3) in K, C and S apartment,respectively. Therefore, it is believed that the indoor concentration of formaldehyde was very serious in new apartment. From these results, it is important that building material which emit low indoor pollutant should be selected for new apartments. In additon, management program for indoor air, such as using an adequate amount of adhesives, should be considered and indoor optimum condition should be maintained in new apartments. Keywords：New apartment, Aldehyde, I/O ratio, Indoor pollutant, Indoor optimum condition