A beam intensity converting film that has sufficient shielding property, sufficient durability, and sufficient heat resistance and that can reduce the extent of radioactivation. An attenuator is constituted by a graphite film placed such that a surface thereof intersects the beam axis of a charged particle beam, the graphite film has a thickness of 1 μm or greater, and the thermal conductivity in a surface direction of the graphite film is equal to or greater than 20 times the thermal conductivity in the thickness direction of the graphite film.