In a gas feeding apparatus for a powder and granular material feeder, in which a powder and granular material 3 supplied to an upper portion tubular hopper 11 is continuously supplied and discharged downward by a powder and granular material feeder provided below the tubular hopper 11, a first feed port 20 for a gas is provided in an upper surface 1a of a bottom plate 1′ on a lower surface of a boss portion for a set of rotary blades 8 of the powder and granular material feeder so that the gas can be fed to a space S between the upper surface 1a of the bottom plate 1′ of the powder and granular material feeder and the lower surface of the boss portion. Further, an annular damming plate 22 is formed on the lower surface of the boss portion on the outer side of the first feed port 20 so that the gas fed into the space S through the first feed port 20 can be fed in a radial direction into the powder and granular material feeder via slits 23, 24 provided around the annular damming plate 22.