The purpose of this research is to reveal the process of the growth of a new venture group in terms of the investment in spin-offs and the instability of the group domain. SoftBank Group (SBG), consisting of SoftBank Corp and its spin-offs, is chosen for our study. Our database includes data sourced from the securities reports of the spin-offs from SoftBank Corp, and the database is used for analysis using the networking analysis software named “Pajek Version2.05”. The followings are found in our study. (1) Spin-off companies have been created in SBG through the allocation of financial resources for each segment. (2) Group domain of SBG has changed by developing the spin-offs at the early stage, and by Merger and Acquisitions at the later stage. (3) SBG creates spin-off companies not only at each company level but at segment (aggregate of companies) level. he implications of our study are as follows. (1) Our study shows the validity to understand the spin-off phenomenon from the point of view of resource allocations rather than that of entrepreneurs. (2) It is suggested that we should observe both spin-offs and the 'maternal' organization to study the change of the group domain. (3) It's implied that another organization model, called Type-F (Fund), might be required. SoftBank Corp plays a role similar to an investment fund in our study. However, there are three limitations of this paper. (1) The analysis is conducted only from the point of financial resources, not that of human resources. (2) The survey didn’t analyze the change of each spin-off. (3) Causal relationships between the development of spin-offs in/as the group and the change of group domain weren't made clear in our study. In order to challenge these limitations, the quantitative analysis for each spin-offs are required to improve the robustness of our study.