To reduce the necessity to change the orientation of a laid patient according to the position of a radiotherapy target.SOLUTION: A radiotherapy apparatus according to the embodiment includes: a bed for supporting a top plate on which a patient is placed such that the top plate is movable along the longitudinal axis of the top plate； a radiation unit for emitting radiation； a support body to which the radiation unit is mounted； and a retention device for supporting the support body. The support body has a recessed part opened to the side of the bed and defining a space which has a size and a shape sufficient for a portion of the top plate at the side of the support body and a portion of the patient to enter.SELECTED DRAWING: Figure 4【課題】放射線治療対象の位置に応じて患者の寝る向きを変更する必要性を低減すること。【解決手段】実施形態に係る放射線治療装置は、患者が載置される天板を、前記天板の長軸に沿って移動可能に支持する寝台と、放射線を照射する照射部と、前記照射部が設けられた支持体と、前記支持体を支持する保持器と、を具備し、前記支持体は、前記寝台側に向けて開口され、前記天板の前記支持体側の一部分と前記患者の一部分とが進入可能な大きさ及び形状を有する空間を形成する凹部を有する。【選択図】 図４
