PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus capable of reducing an air flow passing through a gap in the air flow passing through the gap between an annular rotator and a gantry cover and an air flow passing through the internal space of the annular rotator and exhausted after exchanging heat by a radiator.SOLUTION: This X-ray CT apparatus is provided with: the annular rotator 2 which has an X-ray tube 4, an X-ray detector 5, and the radiator 6 stored in its interior, a vent hole 12 provided in the vicinity of the radiator 6, and an air suction/exhaust port 11 provided at a position oppositely to the vent hole 12 the gantry cover 7 covering peripheral of the annular rotator 2 and having upper air vents 7a and 7b and a plurality of lower air vents 8-10 fans 15 and 16 discharging exhaust in the gap 14 between an inner face of the gantry cover 7 and the outer circumferential face of the annular rotator 2 from the upper air vents 7a and 7b to the outside and baffle plates 19 and 20 provided in the gap 14 in the vicinity of the lower air vents 8-10 of the gantry cover 7, wherein the baffle plate 19 controls the air flow passing through the internal space of the annular rotator 2 and the air flow passing through the gap 14.COPYRIGHT: (C)2010,JPO&INPIT【課題】環状回転体及び架台カバー間の間隙を通る空気と環状回転体の内部を通り放熱器により熱交換されてから排気される空気とのうち、間隙を通る空気の流量を減らすことの可能なX線CT装置を提供する。【解決手段】内部にX線管球4、X線検出器5及び放熱器6が収納され、放熱器6の付近に設けられた通気口12、通気口12に対向する位置に設けられた吸排気口11を有する環状回転体2と、環状回転体2の周囲を覆い上部排気口7a、7b及び下部吸排気口8~10を有する架台カバー7と、架台カバー7内面と環状回転体2の外周面との間の間隙14内の排気を上部排気口7a,7bから外部へ排出するファン15、16と、架台カバー7の下部吸排気口8~10付近の間隙14内に設けられた整流板19、20と、を備え、この整流板19により、環状回転体2の内部の空間を通る空気の流量と、間隙14を通る空気の流量とを制御する。【選択図】図3