Circumscribed choroidal hemangiomas are rare and benign tumors but often have a progressive course and are complicated by retinal detachment and glaucoma. The effectiveness of external radiation for large tumors that are difficult to treat with photodynamic therapy was recently reported; however, few studies have conducted long-term follow-ups. We encountered a case of localized choroidal hemangioma that was treated with proton beam therapy and followed up for 15 years. A 37-year-old man was diagnosed with a 10 × 4 mm circumscribed choroidal hemangioma involving the macular area with retinal detachment. Proton beam therapy was performed at 26.4 Gy relative biological effectiveness (RBE) in 8 fractions. The choroidal hemangioma gradually shrank over three years, and the retinal detachment also improved. A cataract developed on the affected side 11 years after irradiation, and eye coordination issues developed 15 years after irradiation. Glaucoma was not observed during the follow-up period; however, visual acuity did not recover, and the patient developed light perception. Although vision was not preserved, proton beam therapy effectively shrank the tumor and maintained quality of life.