This paper analyzes the impact of the change in telecommunication regulation on network investment such as the integration of telecommunication service. The integration of telecommunication service plays a role of separating the behavior regulation from entrance regulation and reducing a entrance constraints. Therefore, it is expected that the market spill over effect is high through the improvement of behavior regulation such as interconnection regulation, facilities provisions, retail price regulation, bundling, number portability of VoIP. This paper discusses the critical factor affecting the decision making process in respect of the firm level and analyzes the impact path guiding investment and innovation. Finally, the paper proposes the guideline for telecommunications policy.