A composite system for radiation therapy includes a CT scanner for checking the position of an affected portion of a patient to be irradiated, an irradiation apparatus for disposing, on the basis of positional information of the affected portion checked by the CT scanner, the patient at a specific position at which the affected portion is aligned to an irradiation position, and performing irradiation to the affected portion, a common bed used for the CT scanner and the irradiation apparatus, in a state that the patient lies on the common bed and moving means for moving the patient from the CT scanner to the specific position of the irradiation apparatus. The moving means moves the patient on the common bed to the specific position by causing either of linear movement of the CT scanner and the irradiation apparatus, linear movement of the CT scanner and curved movement of the irradiation apparatus, curved movement of the CT scanner and the irradiation apparatus and linear movement of the CT scanner, linear movement of the CT scanner and the common bed, and linear movement of the CT scanner and curved movement of the common bed. With this composite system, at the time of radiation therapy for tumor or the like, the affected portion can be irradiated in a state that the position of the affected portion aligned by a CT scanner is accurately kept. As a result, it is possible to significantly enhance the control of the positional accuracy of the affected portion in radiation therapy and hence to significantly increase the effect of the radiation therapy.