Erythroderma can be caused by many diseases including lymphoma. Patients with erythroderma also exhibit thermal dysregulation, tachycardia and peripheral edema as a result of protein loss. Here, we report a patient with peripheral T-cell lymphoma presenting severe erythema, whose skin manifestation mimicked severe atopic dermatitis. A 40-year-old woman visited the clinic with erythroderma, severe scaling mainly on flexural areas spreading to the whole body. Initial skin biopsy revealed chronic eczematous dermatitis, leading to the first impression of atopic dermatitis. The patient was admitted for several times due to recurrent Staphylococcal infections, and daily dressing with mixture of antibiotic and steroid cream was done during the admissions, but the effect was not remarkable. The patient also experienced severe chilling sensation, peripheral edema with hypoalbuminemia. To evaluate possible infectious condition, abdomino-pelvic CT was done and multiple enlarged lymph nodes were noted. After excisional biopsy at both inguinal lymph node, peripheral T cell lymphoma was diagnosed. PET-CT result suggested peripheral T-cell lymphoma. In spite of systemic and topical antibiotic therapies, the patient expired due to sepsis. We suggest that patients with atopic dermatitis-like clinical features intractable to steroid and systemic symptoms, erythrodermic peripheral T-cell lymphoma should be considered as a differential diagnosis.