||In recent years, research and development of radio systems using quasi-millimeter and millimeter-wave bands has been actively promoted. In millimeter-wave radio systems, especially, an antenna, gateway for radio wave, is an important device that affect the performance of the entire system and are required to be small and have high performance. The authors have previously proposed and investigated a parabolic antenna using a multilayered-printed circuit board (PCB) as a high-gain antenna that is cost-effective, small, lightweight, and easy to modularize. In this study, miniaturization of parabolic reflector formed by multilayered-PCB and antenna gain are investigated. As a result, it was confirmed that the maximum gain of 20.8 dBi were obtained in the miniaturized antenna of 38% in volume ratio compared to the full-sized conventional antenna.