I have been working on a ground-based Cosmic Microwave Background (CMB) experiment, POLARBEAR, aiming to observe polarization with a high sensitivity. Our goal is to reveal the early history of our universe through observing polarization modes created by the inflation. The POLARBEAR telescope is currently observing in the Atacama Desert, Chile (elevation of 5,200 m). Meanwhile, we are preparing for an upgraded experiment, POLARBEAR-2 with a higher sensitivity. To achieve the required sensitivity, we will install more than 7,000 superconducting detectors at cryogenic temperature. My research focuses on how we can achieve such large detector arrays. This study aims not only to conduct a groundbased experiment, but also to perform a Japaneseled satellite experiment, LiteBIRD.