Japan Aerospace Exploration Agency (JAXA) has been conducting studies on Space Solar Power Systems (SSPS) using microwave and laser beams for years since FY1998 organizing a special committee and working groups. Current SSPS study undertaken by JAXA consists of three main subjects, SSPS concepts and architectures study, technology demonstration plan-making and elemental technology development. In SSPS concepts and architectures study, system concepts and architectures of commercial type of microwave based SSPS (M-SSPS) and laser based SSPS (L-SSPS) has been studied for years. In this study, a major focus is on identifying system concepts, architectures and key technologies that may ultimately produce a practical and economical energy source. In the study of technology demonstration plan-making, system design of tens of kW class Technology Demonstration Satellite and Ground Energy Transmission Experiment are conducted. In elemental technology development study, several key technologies which are needed to be developed in appropriate R&D roadmap are investigated. This paper presents the results of these study effort of JAXA and the most promising SSPS concepts, including their key technologies.