We experienced a patient who first visited the Department of Otolaryngology with the chief complaint of tonsillitis, with subsequent eruption during the observation period. On the basis of these findings, a diagnosis of Sweet's disease was made. The patient was a 28-year-old female who complained chiefly of pharyngalgia and fever. Antibiotic therapy, which was indicated in accordance with the diagnosis of tonsillitis was ineffective in relieving the symptoms. A skin biopsy was performed because of complications including painful nodular skin lesions, arthalgia and swelling of the joints. The skin biopsy results facilitated a definitive diagnosis of Sweet's disease. The patient's expression of adhesion molecules associated with peripheral neutrophils was within the normal range. We regarded the causative factor as a hypersensitive reaction due to tonsillitis, and conducted a tonsillectomy.