The present invention relates to an apparatus for measuring floating microorganisms in a gas phase in real time using a system for dissolving microorganisms and adenosine triphosphate (ATP) illumination, and to a method for detecting same. The measuring apparatus includes a particle classifying apparatus for collecting floating microorganisms and being coated by an ATP reaction illuminating agent; a system for dissolving microorganisms for dissolving the microorganisms and extracting ATP; and a light receiving device for detecting light generated from the reaction of the extracted ATP by the system and the ATP reaction illuminating agent coated on the particle classifying apparatus. According to the detection method using ATP organism illumination, the floating microorganisms in the gas phase can be readily detected and the detection can be automatically conducted in real time without manual labor.