Protons have an ideal characteristic for radiotherapy in terms of dose distribution, and the clinical values of proton radiotherapy have been recognized over thirty years. The outstanding clinical results for the selected categories of patients such as uveal melanoma, sarcoma of the skull base and/or the cervical spine, and relatively slow-growing, intracranial lesions treated with proton therapy have already been well reported through many articles. In recent years, the technological development has produced proton accelerator that generates protons appropriate for the treatment of deep-seated tumors, and isocentric gantry system. It will be necessary however, to evaluate and establish the efficacy of proton radiotherapy for tumors that have not previously been studied during the next decade. The number of treatment facilities has been steadily increased over the world. Proton radiotherapy is expected to play an important role in cancer treatment in the near future.