A pillbox-type RF window having an input/output window in a microwave tube, the pillbox-type RF window includes a disc-shaped member having a metallization layer formed on an outer peripheral portion of a disc-shaped ceramic body; a pair of ring-shaped members constituted by metal bodies having substantially the same outer diameters as the disc-shaped member, arranged to sandwich the disc-shaped member from both sides, and integrated with the outer peripheral portion of the disc-shaped member; a tube-shaped member constituted by a metal body having an inner diameter substantially equal to the outer diameters of the pair of ring-shaped members and the disc-shaped member, for holding the pair of metal components and the disc-shaped member on an inside thereof; and a restriction member for suppressing rotation between the ring-shaped members and the tube-shaped member.