The current interest in atmospheric particulate matter (PM) is mainly due to its effect on human health. Exposure to outdoor PM is associated with a wide range of adverse health effects. Indoor air contains a complex mixture of bioaerosols such as bacteria, fungi and allergens. Children are known to be more susceptible to the exposures of PM and bioaerosols which are represented by airborne bacteria, fungi, and allergens. This study is to assess concentrations of the atmospheric PM and bioaerosols indoors and outdoors at 15 daycare centers for children located in Seoul. Particles were measured indoors and outdoors with automatic particle monitoring using beta radiation absorption. Airborne bacteria and fungi were sampled by Anderson sampler. Analysis shows that average indoor PM10 was 95.7 μg/m3 (SD 26.6 μg/m3) and average level of airborne bacteria and fungi were 575.0 CFU/m3 (SD 431.6 CFU/m3) and 77.9 CFU/m3 (SD 45.6 CFU/m3), respectively. Finally, efficient ventilation and effective air cleaning strategies are necessary to reduce indoor concentrations of particles and bioaerosols. Keywords : Daycare, PM, Bioaerosol, Air purifier