The purpose of present invention is to obtain a beam monitor for particle beam therapy device that is capable of confirming beam position during test irradiation and monitoring whether charged particle beam run off the designed beam track or not even during real irradiation.The beam monitor (34) for particle beam therapy device of present invention has: a fluorescent screen (17) arranged on the designed beam track (duct center line (25)) of the charged particle beam and having an opening part (18) where the charged particle beam can pass through a lid part (19) opening and closing the opening part (18) and coated by fluorescent paint a lid part moving mechanism (43) moving the lid part (19) to open and close the opening part (18) a camera (21) arranged to observe the surface of the fluorescent screen (17). During test irradiation, the opening part (18) is covered by the lid part (19).本發明之目的在於獲得一種粒子射線治療裝置用之射束監視器,係在試驗照射時能夠確認射束位置,且在實際照射中亦能夠監視帶電粒子射束是否偏離射束設計軌道。本發明之粒子射線治療裝置用之射束監視器(34)係包括:螢光板(17),係配置於帶電粒子射束的射束設計軌道(導管中心線(25))上,並且具有設成為帶電粒子射束能夠通過之開口部(18);蓋部(19),係將開口部(18)予以開閉,並且塗覆有螢光塗料;蓋部移動機構(43),係以開口部(18)開閉之方式移動蓋部(19);以及攝影機(21),係配置成觀察螢光板(17)的表面;其中,在試驗照射時,藉由蓋部(19)覆蓋開口部(18)。15‧‧‧真空導管16‧‧‧窗17‧‧‧螢光板18‧‧‧開口部19‧‧‧蓋部20‧‧‧馬達21‧‧‧攝影機25‧‧‧導管中心線(射束設計軌道)26‧‧‧攝影機軸27‧‧‧資訊處理器34‧‧‧射束監視器sige‧‧‧異常檢測訊號
