Citizen satisfaction levels with public service have become a key indicator in evaluating a nation's policy capability; as such, it has become important to realize citizen-centered public service that enhances the satisfaction of citizens. Governments need to adopt new and creative methods to respond to changes and redefine the conditions of their policy processes. This study reviews the effectiveness of utilizing open innovation by design thinking for policy processes, and aims to detail the conditions for a policy process geared towards citizen-centered public service. The study reviews open innovation as a means of overcoming the insular tendencies of organizations, and also reviews the advantages of design thinking in identifying the diversified needs of citizens and coordinating their interests. Based on those, we conducted a case study and applied open innovation by design thinking for policy processes. The results revealed that key conditions include cooperation among designers, the diversification of communication channels between internal and external organizations, the joining of citizen experiences, repeated verification of citizen needs, and visualization of the whole progression. Such conditions are principal factors that contribute to citizen orientation and participation, and are expected to play a conducive role in the realization of citizen-centered public service in the future.