An air flow drying device comprising: a vertical cylindrical housing, a raw material supply portion adapted to supply a raw material containing moisture into the housing, a disc-shaped rotator that is disposed below the raw material supply portion and is adapted to rotate on a vertical rotating axis, a pulverization member that is disposed on an outer periphery of the rotator and is adapted to pulverize the raw material into a granule, a hot wind supply portion that is adapted to supply a hot wind below the rotator in the housing, and a discharge portion that is adapted to discharge the granule from an upper portion of the housing, a fan connected to the discharge portion, and a bearing portion that is disposed on a bottom portion of the housing and that supports a shaft portion of the rotator, such that the granule can be pulverized by the pulverization member, dried by the hot wind and discharged, wherein the housing has an annular liner that opposes the pulverization member, and wherein the hot wind supply portion has: an outer circumferential portion where the hot wind flows contacting an outer circumferential surface of the liner; and an inner circumferential portion that guides the hot wind to a gap between the pulverization member and the liner through an opening portion below the liner, characterized in that the device further comprises an outside air inlet adapted to introduce outside air into the housing from below the hot wind supply portion, wherein the inner circumferential portion has an annular portion that opposes an inner wall of the housing to form a circumferential wall of the inner circumferential portion and a horizontal portion that extends horizontally from the upper end of the annular portion, wherein an upper end of the annular portion and the horizontal portion approach a lower surface of the rotator to form a gap, wherein an inner circumferential end of the horizontal portion approaches the shaft portion to form a gap, and wherein the device is configured such that, when the fan is driven, outside air flows into the housing via the outside air inlet, flows in a gap between the horizontal portion and the shaft portion and in a gap between the horizontal portion and the lower surface of the rotator, joins the hot wind in the inner circumferential portion, and ascends. a vertical cylindrical housing, a raw material supply portion adapted to supply a raw material containing moisture into the housing, a disc-shaped rotator that is disposed below the raw material supply portion and is adapted to rotate on a vertical rotating axis, a pulverization member that is disposed on an outer periphery of the rotator and is adapted to pulverize the raw material into a granule, a hot wind supply portion that is adapted to supply a hot wind below the rotator in the housing, and a discharge portion that is adapted to discharge the granule from an upper portion of the housing, a fan connected to the discharge portion, and a bearing portion that is disposed on a bottom portion of the housing and that supports a shaft portion of the rotator, such that the granule can be pulverized by the pulverization member, dried by the hot wind and discharged, wherein the housing has an annular liner that opposes the pulverization member, and wherein the hot wind supply portion has: an outer circumferential portion where the hot wind flows contacting an outer circumferential surface of the liner; and an inner circumferential portion that guides the hot wind to a gap between the pulverization member and the liner through an opening portion below the liner, characterized in that the device further comprises an outside air inlet adapted to introduce outside air into the housing from below the hot wind supply portion, wherein the inner circumferential portion has an annular portion that opposes an inner wall of the housing to form a circumferential wall of the inner circumferential portion and a horizontal portion that extends horizontally from the upper end of the annular portion, wherein an upper end of the annular portion and the horizontal portion approach a lower surface of the rotator to form a gap, wherein an inner circumferential end of the horizontal portion approaches the shaft portion to form a gap, and wherein the device is configured such that, when the fan is driven, outside air flows into the housing via the outside air inlet, flows in a gap between the horizontal portion and the shaft portion and in a gap between the horizontal portion and the lower surface of the rotator, joins the hot wind in the inner circumferential portion, and ascends.