Abstract: A lung phantom unit for radiotherapy according to an embodiment of the present disclosure may arrange, at a location not affected by a magnetic field, a phantom driving cylinder and a driving device which may move a lung mimic and a tumor mimic in a lung simulation block. The lung phantom unit may be used for general purpose even as a phantom for MRI-based and CT image-based radiotherapy. Since lung and tumor motions are implemented by air injection, it may be possible to precisely measure the motion and volume change of a lung according to subtle changes in air pressure so that customized radiotherapy suitable for a patient having various breathing patterns is possible.