We report a case of Beau's lines at even intervals and onycholysis caused by chemotherapy. The patient with a diffuse large cell B cell lymphoma (DLBCL) stage A underwent combination chemotherapy consisting of R-CHOP (Rituximab, cyclophosphamide, doxorubin, vincristine, predonisolone) every three weeks (21-day intervals) six times. As he was treated with R-CHOP, he noticed each Beau's lines (transverse groove ) on all 20 nails each time. In addition, he had onycholysis caused by cyclophosphamide and doxorubicin treatment. Two months after discontinuation of chemotherapy, Beau's lines disappeared.