現代科技日新月異，人類的太空活動也展現迥異於以往的面貌。太空科技不僅延伸到宇宙，另一方面也深入地表影響人類生活，諸如衛星傳送、新創產業、軍事技術等。連結虛擬和現實的宇宙空間，現行國際法必須處理嶄新議題的太空垃圾、太空國際法制化、太空資產保護等。同時間，從太空發射的低軌衛星訊息傳送、氣象觀測、衛星遙測等，也與一國內的太空法規範息息相關。這些都挑戰目前主權國家在國際社會的行為，以及在國內制定太空政策的想像。本文取日本太空發展之例，從公共財理論的概念分析太空集體財和私有財的內涵。發現由於太空的研發耗資龐大、跨領域、高度專業等特殊性下，國家們必須攜手合作建構太空集體財，凸顯太空外交的重要性。其次，以往太空科技往往運用於軍事，然現今逐漸擴大到民生，造就太空軍民兩用產業的活絡。換言之，各國民間太空產業的私有財活動，受到國家制定的法律規範，同時企業也以民間融資提案（Private Financial Initiative）方式幫助國家解決政府失靈問題。無論是太空集體財或私有財都出現有「公私混合」的性質，與傳統財貨定義的性質有所不同，說明太空發展的挑戰和新議題。

Modern technology is advancing with each passing day, and human space activities are also showing a completely different appearance from the past. Aerospace technology not only extends to the universe, but also profoundly affects human daily life, such as satellite transmission, emerging industries, and military technology. In order to regulate these human activities in space, the current international law must deal with new issues such as space junk, international legalization of space, and protection of space assets. At the same time, low-orbit satellite information transmission, meteorological observation, satellite telemetry, etc. launched into space are also closely related to a country's domestic space regulations. These technological innovations and the resulting activities and regulations continue to challenge current assumptions about the boundaries of sovereign states and their behavior in the international community, as well as their considerations in space policy making. Taking Japan's space development as an example, this paper analyzes the connotation of toll goods and private goods in space from the framework of the theory of Public Goods. It is found that due to the enormous cost of aerospace R&D and its cross-domain, highly specialized nature, states must work together to build space toll goods. This highlights the importance of space diplomacy. Moreover, in the past, aerospace technology was often only used in the military, but now it is gradually expanding to the field of people's livelihood, creating the vitality of the space dual use technology. That is to say, the civil activities of the aerospace industry of various countries are regulated by the laws formulated by the state on the one hand, and on the other hand, enterprises also enter the public domain by assisting the state to solve the problem of market failure by means of Private Financial Initiatives. Whether it is toll goods or private goods in space, there is a ‘public-private hybrid’ in nature, which is different from the traditional understanding defined by the Theory of Public Goods. This also illustrates the challenges and new issues of space development.