This is a single arm phase II study, in which maximum 3 cycles of nivolumab (240 mg fixed dose every 2 weeks) is administered for T2- or T3-node negative esophageal squamous cell carcinoma, before curative operation.

Inclusion Criteria:

1. Histologically confirmed esophageal squamous cell carcinoma
2. Clinical stage T2N0 (invasion to muscularis propria) or T3N0 (invasion to adventitia)
3. ECOG performance 0 or 1
4. Age 19 years or older

Exclusion Criteria:

1. Prior therapy (operation, radiotherapy, immunotherapy, or chemotherapy) for esophageal cancer
2. Ineligibility or contraindication for esophagectomy
3. Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy (in dosing exceeding 10 mg daily of prednisone equivalent) or any other form of immunosuppressive therapy within 7 days prior to the first dose of study drug.
4. Has active autoimmune disease that has required systemic treatment in the past 2 years (i.e. with use of disease modifying agents, corticosteroids or immunosuppressive drugs).
5. Has severe hypersensitivity and adverse events (≥Grade 3) to nivolumab and/or any PD-1/PD-L1 inhibitors.