A radiotherapy apparatus for an animal comprises a treatment part including an accommodation space for placing an animal, an irradiation part including an electron generator and a linear accelerator coupled to one side of the electron generator and disposed in a direction perpendicular to the treatment part, the linear accelerator being configured to emit radiation toward the treatment part, and an image acquisition part located at a preset interval from the treatment part along an irradiation direction of the radiation and configured to obtain an image of an irradiation area when the radiation is applied, wherein the radiation has an output of 1 MeV to 2 MeV so as to be applied to a diseased part located within a predetermined distance range from epidermis of the animal.