Proton beam therapy (PBT) has made it possible to deliver a higher concentration of radiation to the tumor by its Bragg-peak, and is easy to utilize due to the fact that its biological characteristics are identical with X-rays. PBT has a half-century history, and more than 40,000 patients have been reported as having had treatments with proton beams worldwide. The historic change to this therapy occurred in the 1990s, when the Loma Linda University Medical Center began its clinical activity as the first hospital in the world to utilize a medically dedicated proton therapy facility. Since then, similar hospital-based medically dedicated facilities have been constructed. Results from around the world have shown the therapeutic superiority of PBT over alternative treatment options for ocular melanoma, skull base sarcoma, head & neck cancer, lung cancer,esophageal cancer, hepatocellular carcinoma, and prostate cancer. PBT is expected to achieve further advancement both clinically and technologically.