Nitrogen dioxide $(NO_2)$ has been regarded as one of the main elements among air pollutants, and we measured $NO_2$ levels of near gas range, kitchen, living room and outdoor on 489 apartments in Pusan area. $NO_2$ were sampled by using Palmes tubes (diffusion tube sampler) during August 16-25, 1995 (summer) and January 15-29, 1996 (winter), respectively. Authors wanted to know comparison of $NO_2$ levels in summer and winter, $NO_2$ levels categorized by variables, and variables affected to $NO_2$ levels. According to this study, we conducted to establish the degree of indoor-outdoor air pollution of urban apartments in Korea and methods to reduce indoor air pollution. The results of this study were summarized as follows: 1) Mean $NO_2$ levels of near gas range, kitchen, living room, and outdoor were $25.9{\pm}10.0ppb,\;23.3{\pm}8.0ppb,\;19.9{\pm}6.1ppb,\;and\;19.0{\pm}6.0ppb$ in summer, and $34.5{\pm}16.8ppb,\;28.2{\pm}13.4ppb,\;25.3{\pm}12.5ppb,\;21.8{\pm}9.8ppb$ in winter, respectively. 2) Mean $NO_2$ levels according to the floor levels were not significantly different in summer, and in winter, $NO_2$ levels were decreased as the floor levels were increasing, but those were increased above 16th floor. 3) Variables showing significant correlation(p<0.05) with $NO_2$ levels were as follows; Summer: floor level, family size, number of family during a meal, number using gas range during rice cooking per day, and natural ventilation. Winter: floor level, family size, number of person who have been respiratory disease in a house, number of family during a meal, total number of meals, and number using gas range during rice or side-dish cooking per day. 4) We suggest that the methods of reducing indoor $NO_2$ levels are ventilation during cooking, complete combustion, decreasing number and time of cooking, and substitution of fuels.