Autoimmune disease (such as rheumatic diseases) or allergic disease (such as atopic dermatitis) is induced by breaking of balance between Th1 and Th2 T cells. Stem cells can keep the balance between Th1 and Th2, enabling treatment for the above diseases. In particular, autoimmune diseases comprise over 100 kinds of diseases. Their complications can be life-threatening. Such risks are intractable. Thus, the trend of treatment employing stem cells is increasing. Stem cells can keep immunologic function normally by improving the reduced immunologic function or normalizing excessively exacerbated immunologic function.