A multi-disc air diffuser according to the present invention comprises a bolt having a vent groove formed in a longitudinal direction thereof; a plurality of discs, each of the discs having a bolt joint section to be passed through the bolt, an air room for holding the air supplied through the vent groove, and a nozzle section having a plurality of nozzles which are arranged in an end part of the air room at a regular size and intervals, wherein the lower surface of each of the discs is more than the upper surface thereof and the outer circumference surface of each of the discs is formed to be inclined; and a backflow prevention section for joining to an end part of the bolt to adhere closely the discs to one another, connecting the vent groove to an air supply pipe, and having a check valve to prevent the air flowing backward from the vent groove to the air supply pipe.