A method for preventing or treating atopic dermatitis of a patient by covering the patient itself or a patient's area affected by the atopic dermatitis, filling a covered space with positive ions composed of H + (H 2 O) m (m being any integer) and negative ions composed of O 2 - (H 2 O) n (n being any integer) generated as a result of discharge in an atmosphere, and bringing the positive ions and the negative ions into contact with a skin surface of the patient and a medical device for preventing or treating atopic dermatitis by covering a patient itself or an affected area, filling a covered space with positive ions composed of H + (H 2 O) m (m being any integer) and negative ions composed of O 2 - (H 2 O) n (n being any integer) generated as a result of discharge in an atmosphere, and bringing the positive ions and the negative ions into contact with a skin surface of the patient.
