To realize high data rate satellite communication service for future multi-media applications, the Wideband InterNetworking engineering test and Demonstration Satellite (WINDS) has been developed by the Japan Aerospace Exploration Agency (JAXA). WINDS is equipped with Ka-band transmitting and receiving Active Phased Array Antennas (APAAs), which can flexibly establish communication to any area electronic beam scanning. Before development of the APAAs flight model, we developed partial models of transmitting and receiving APAAs to evaluate their beam performance. We verified the basic performance such as radiation pattern, beam scanning, and input-output performance. This paper describes the design of the APAAs and development results of a partial model.