In this paper, we introduce a 5G K-Simulator consisting of a link-level simulator (5G K-SimLink), a system-level simulator (5G K-SimSys), and a network simulator (5G K-SimNet). The 5G K-Simulator is open source to solve the waste of human and material resources consumed in simulator development in the continuous management and performance analysis / verification of wireless communication technology. The code of the 5G K-Simulator is developed with a modular and flexible methodology so that users can easily change or extend it according to their purpose. In addition, we provide a web-based simulator platform that allows users to more easily use. The 5G K-Simulator assures objectivity through verification by a beta test of experts group. Using 5G K-Simulator, universities, research institutes, and industries can easily perform the development of 5G technology and verification of it. Moreover, it can also be used to develop vertical industry and application services technologies related to 5G wireless / mobile communication. Furthermore, we hope that it will become the basis of the simulator for technical analysis and verification of communication system after 5G.