Towards a sustainable society, design of artifacts must be optimized with limited resources on the earth while keeping our life. In order to realize it, I emphasize openness of design information. In this paper, I discuss needs for openness of design information and methods to realize it. I argue why design information should be open and what benefits will result by opening and sharing design information. Opening design information looks difficult considering the current structure of the industries, but I show some possibilities from two aspects of design activities. In software design, open source software is getting accepted as a way of developing software products. I overview it and analyze how it can be applied to artifact design. Then I discuss how such an environment can be built. Identification, representation, and sharing mechanism are crucial. Lastly I summarize discussion with people in the design community. Many people disagree with opening design information, but I dispute ...