The objective of this study is to quantify the levels of airborne bacteria in pig building according to pig housing type. Mean concentration of airborne bacteria in the housing room of gestation/farrowing pigs were 3,690(±1,528)cfu m-3 in spring, 10,145(±4,266)cfu m-3 in summer, 1,546(±835)cfu m-3 in autumn, and 2,582(±916)cfu m-3 in winter, respectively. Mean concentrations of airborne bacteria in the housing room of nursery pigs were 11,628(±5,624)cfu m-3 in spring, 36,054(±13,260)cfu m-3 in summer, 2,743(±1,688)cfu m-3 in autumn, and 4,075(±2,300)cfu m-3 in winter, respectively. Mean concentrations of airborne bacteria in the housing room of growing/fattening pigs were 34,025(±8,652)cfu m-3 in spring, 36,619(±10,234)cfu m-3 in summer, 10,230(±3,521)cfu m-3 in autumn, and 26,208(±5,248)cfu m-3 in winter, respectively. As a result, mean concentrations of airborne bacteria in terms of pig housing type were highest in growing/fattening housing room followed by nursery housing room and gestation/farrowing housing room (p<0.05). The pig building showed the highest levels of airborne bacteria in summer followed by spring, winter and autumn (p>0.05). Overall airborne bacteria which have particle size over 2.1㎛ (stage 1~stage 4) accounted for approximately 80% compared to total airborne bacteria regardless of pig housing type. The predominant airborne bacteria in pig building were Micrococcus spp., Brevibacillus spp. and G(+) Bacillus. Keywords : airborne bacteria, pig building, gestation/farrowing, nursery, growing/fattening