In order to design the indoor air quality on bio-aerosol appropriately, it is necessary to clarify the actual status of contamination caused by microorganism such as bacteria and fungi in indoor environments. This paper reports the results obtained from the field measurements on the indoor airborne bacteria and fungi. The major results are shown as follows. (1) Both airborne bacterium and fungus concentration are satisfied with AIJES-A002-2005 (Architectural Institute of Japan Environmental Standards, 500cfu/m3 for bacteria, 50cfu/m3 for fungi). (2) It is considered that the main contaminant source of bacteria is in indoors, while that of fungus is in outdoors in the case of air-conditioned office building. (3) As for bacteria, it became clear that more than half of bacteria are micrococcus. As for fungi, Cladosporium, Penicillium, Aspergillus and so forth were found in indoors.