Afatinib is an irreversible second-generation tyrosine kinase inhibitor. It is used to treat epidermal growth factor receptor (EGFR) mutation-positive lung adenocarcinoma. The most well-known side effects associated with afatinib are diarrhea, rashes or acne and stomatitis. Herein, we present a case of skin toxicity that developed in the late phase of afatinib treatment. A 51-year-old, non-smoker woman diagnosed with EGFR deletion-19 mutant advanced lung adenocarcinoma. Afatinib was initiated as the first-line treatment. At the twelfth treatment month, Grade-2 acneiform dermatitis, paronychia, and HFS developed. Despite the interruption or discontinuation of afatinib treatment and local/systemic steroid treatments, the lesions did not regress. The patient was responsive to afatinib; however, the treatment was discontinued in the eighteenth month of treatment. The treatment response may be predicted by the severity of skin toxicities owing to afatinib. They occur in the early treatment phase and are commonly observed at the Grade 1-2 level.