PROBLEM TO BE SOLVED: To provide a horizontal rotary container type powder processing device capable of significantly improving airtight accuracy in a cylindrical rotary container, and very easily processing powder under a vacuum atmosphere. SOLUTION: This horizontal rotary container type powder processing device 1 includes: the cylindrical rotary container 2 disposed rotatably on a horizontal shaft; a vacuum atmosphere forming means 3 mounted on the cylindrical rotary container 2 for discharging a gas in the cylindrical rotary container 2; an opening end 4 disposed on one end of the cylindrical rotary container 2 and constituting a supply opening and a discharge opening of the powder; a powder supply pipe body 5 inserted into the opening end 4, and movable in the axial direction same as an axis of the cylindrical rotary container 2; and a rotary valve 6 rotatably mounted on an outer face of the powder supply pipe body 5. The rotary valve 6 is brought into contact with the opening end 4 in accompany with the movement to a cylindrical rotary container 2 side of the powder supply pipe body 5 to seal the same, and is rotatable in accompany with the rotation of the cylindrical rotary container 2. COPYRIGHT: (C)2010,JPO&INPIT