Disclosed is a tumor surface dose enhancing radiotherapy apparatus using a magnetic field, including a radiation beam generating unit that irradiates a radiation beam towards a tumor of a patient, a magnetic field generating unit that forms a magnetic field that is parallel to the radiation beam between the radiation beam generating unit and the tumor of the patient, and a control unit that controls a surface dose of the tumor by adjusting an intensity and an effective area of the magnetic field of the magnetic field generating unit.