In recent NPO theories, there are many theorists who consider NPOs as CSOs (Civil Society Organizations). They consider NPOs as important actors constructing civil society and civil public sphere, a priori. In this context, contemporary "civil society" concept means the sphere of voluntary associations and the network of voluntary associations, other than the state and the market. In understanding that civil society concept, many sociologists like K. Hasegawa and Y. Satou apply Habermas's civil society (Zivil gesellschaft) which form civil public sphere characterized by free and open communication and discussion. But, when we observe the actual NPOs in the present Japan, many NPOs suffer organizational isomorphism pressures which make NPOs become quasi-nongovermental organizations and normal business organizations, because of the increase of contracts from the state to NPOs and the increase of NPOs' commercial activities in the market. So Japanese NPOs are on the verge of the alienation from the role of civil society organizations. So we must question the concrete condition and the prosess of NPOs constructing the public sphere actually. Then in this paper, at first I will discuss the ownership of NPOs by reviewing the social enterprise theory of EMES network. European social enterprise theory have criticized American institutional choice theory which have been led by mainly H. Hansmann and regards multi-stakeholder organization as important. In the second, I will focus on volunteers as an important stakeholder who construct civil public sphere. Because volunteers have the potential to create the sphere of intimacy, then volunteers can touch the needs of people deeply. Then at last I argue that open governance structure and active and effective volunteers are very important in order to construct civil public sphere on the basis of NPOs.