The present invention provides a compound of formula (I) having an excellent JAK3 inhibition activity and being useful as an active ingredient of an agent for treating and/or preventing various immune diseases including autoimmune diseases inflammatory diseases, and allergic diseases. The compound according to the present invention has an inhibition activity against JAK3 and is thus useful as an active ingredient of an agent for treating or preventing diseases caused by undesirable cytokine signal transmission (e.g., rejection during organ/tissue transplantation, autoimmune diseases, multiple sclerosis, rheumatoid arthritis, psoriasis, asthma, atopic dermatitis, Alzheimer's disease, and atherosclerotic disease), or diseases caused by abnormal cytokine signal transmission (e.g., cancer and leukemia).