This paper describes the performance of NASDA＇s various space solar cells by comparing flight data and ground test data. We first present the flight data from the Solar Cell Monitor on Engineering Test Satellite-VI. We then describe the ground irradiation tests of solar cells performed in collaboration with the Japan Atomic Energy Research Institute. Then discuss the radiation effects on solar cells, and present other flight data of solar cells and optical data of the coverglass from other satellites in addition. Finally, we describe the future plan to obtain flight data on various solar cells.