Provided is an air cavity module for a planar type filter operating in millimeter-wave frequency bands. The air cavity module includes: the planar type filter operating in the millimeter frequency bands; an air cavity having open side and top surfaces to mount the planar type filter therein; and an air cavity cover closing up the open top surface of the air cavity to allow the transmission of signals from and into the planar type filter. The air cavity module can lessen both transmission loss and radiation loss to improve the characteristics of the filter that operates in the millimeter-wave frequency bands.