A 61-year-old male suffered from intrahepatic cholangiocarcinoma in S7 lesion(90 mm diameter), diagnosed by hepatic tumor biopsy. As PET-CT showed para-aortic lymph node metastasis(cT3N1M1, cStage ⅣB), and judged to be unresectable, he received neoadjuvant chemotherapy of gemcitabine, cisplatin, and S-1(GCS). After 7 courses of GCS, CT showed partial response of the primary tumor and PET-CT showed decreased accumulation of FDG at para-aortic lymph node. Resectability was reexamined and the patient underwent S7 extended subsegmentectomy as conversion surgery. Furthermore, after the surgery, he received adjuvant chemotherapy of S-1 for 6 months, and he remained relapse-free for the next 2 years. Cholangiocarcinoma is one of the most poorly prognosed type cancer. Conversion surgery for unresectable intrahepatic cholangiocarcinoma is frequently reported, but there are still few reports of GCS as neoadjuvant chemotherapy. Here, we report a case of unresectable intrahepatic cholangiocarcinoma that was successfully treated with GCS and underwent conversion surgery.