We report a case of locally advanced unresectable(UR-LA)pancreatic cancer in a patient who underwent conversion surgery after FOLFIRINOX and proton beam therapy(PBT)combined with S-1. A 68-year-old woman was referred to our hospital for a pancreatic tumor. The abdominal CT scan revealed a 40mm pancreatic body tumor with an abutment(>180°) of the celiac artery and the superior mesenteric artery. Moreover, the tumor was classified as UR-LA with a contact to the abdominal aorta. The tumor was histologically diagnosed as adenocarcinoma via an endoscopic ultrasound-guided fine-nee- dle aspiration. After 2 courses of FOLFIRINOX, PBT(50 GyE/25 Fr)combined with S-1 were administered. The tumor shrunk to 30mm at the CT scan. After 5 courses of FOLFIRINOX, the tumor reduced to 20 mm. No distant metastasis or malignant cells in abdominal washing cytology was detected using staging laparoscopy. Then, distal pancreatectomy with celiac axis resection(DP-CAR)was performed. According to the General Rules for the Study of Pancreatic Cancer(7th edition)from Japan Pancreas Society, the histological findings were suggestive of ypT3, ypN0, R0, and Grade 3 histological effect. The patient had a Grade A delayed gastric emptying post-operation. He was discharged 35 days after the surgery and has been alive without recurrence on imaging for 11 months post-operation.