A 70-year-old man was admitted for lymph node metastasis detected by FDG-PET/CT showing a mass 10mm in diameter. He had a history of a distal gastrectomy for advanced gastric cancer and was administered postoperative adjuvant chemotherapy consisting of 2 courses of TS-1 with CDDP and TS-1 only for 1 year. Lymph node recurrence was diagnosed and resected 4 years after the initial surgery. Histological examination revealed lymph node metastasis of the gastric cancer. He was administered adjuvant chemotherapy using TS-1 and has been followed-up without recurrences for 17 months after the second operation. We reported a case in which FDG-PET/CT was potentially beneficial for the diagnosis of the postoperative small lymph node metastasis.