The present invention relates to a composition for preventing, treating or alleviating atopic dermatitis comprising an immunosuppressant and a transglutaminase 2 inhibitor as active ingredients. Conjoint administration of an immunosuppressant and a transglutaminase 2 inhibitor according to the present invention makes it possible to achieve far better therapeutic effects than with administration of either an immunosuppressant or a transglutaminase 2 inhibitor alone, since there is a reduction in the dose of an immunosuppressant which is difficult to administer for a long time because of side effects and with which, when discontinued, lesions are liable to become exacerbated to the original state, and since an immunosuppressant is mixed with a transglutaminase 2 inhibitor which in some patients has a lackluster effect in treating atopic dermatitis.