We report 4 patients who underwent proton beam therapy after debulking surgery for unresectable local recurrence of rectal cancer. Case 1: A 55-year-old man underwent radiotherapy and systemic chemotherapy for local recurrence; however, the lesion exhibited evident regrowth. Combination therapy of debulking surgery, omental wrapping of the residual tumor as a spacer, and postoperative proton beam therapy was performed. He died of lung metastasis after 24 months. Case 2: A 79- year-old woman who underwent surgical resections and radiotherapy twice in a previous hospital was referred to our hospital. Similar to that in case 1, proton beam therapy after debulking surgery and omental wrapping was performed. She died of lymph node metastasis after 31 months. Case 3: A 75-year-old man was diagnosed with unresectable local recurrence of rectal cancer. He underwent combination therapy and is doing well without any recurrence for 43 months. Case 4: A 57-yearold woman was also diagnosed with unresectable local recurrence. She underwent the same combination therapy after systemic chemotherapy. She died of lymph node metastasis after 11 months.