X-rays transmit through a vacuum duct along an axial direction of the vacuum duct. A plurality of first partition plates are disposed in the vacuum duct. Each of the first partition plates is formed with a first through hole at a central area thereof. The first partition plates divide the inner space of the vacuum duct in the axial direction and define a plurality of partitioned spaces. A plurality of second partition plates are provided each corresponding to each of the first partition plates. The second partition plate is disposed at a certain gap relative to a corresponding one of the first partition plates, each of the second partition plates being formed with a second through hole at a central area thereof, the X-rays transmitting through the vacuum duct passing through the second through hole. A support member connects the second partition plates together and fixes a relative position of the second partition plates. A support member driving unit supports the support member in the inner space of the vacuum duct and drives the support member to move the second partition plates in accordance with a swing of a central axis of a flux of the X-rays transmitting the inner space of the vacuum duct. A film hermetically seals an output end of the vacuum duct and transmits the X-rays therethrough.