There has been a limit to the development of sustainable public designs due to the lack of procedural publicness in the public regeneration projects of abandoned urban railway sites increasing nationwide. Therefore, this study intends to propose a strategy for expanding publicness in urban regeneration projects. For the planning and implementation stages of urban regeneration public design, representative cases were analyzed according to the three evaluation dimensions of publicness: citizen participant, democratic governance, and institutional policy support. The case analysis was compared to the degree of expansion of publicness according to the evaluation index, and by synthesizing this, a strategy for publicness was investigated. In order to expand the publicness of urban regeneration public design projects, it is necessary to present the best site utilization plan based on the independent participation of civil society from the stage of utilization planning of the abandoned railway site. Together, a democratic governance system that can maximize public-private collaboration orientation is required, and an integrated policy at the institutional level is required to connect disconnected urban organizations and become a strategic base for public design for spreading urban regeneration. The study can be used as an evaluation dimension for the publicness of the urban regeneration public design project using the abandoned railway site and is meaningful in that it proposes a procedural and content methodology for public values that should be considered when promoting urban regeneration projects.