The procedural assistance service, which started as a pilot project to protect the procedural rights of people with psychiatric disabilities who are involuntarily hospitalized, was converted into a main project. The 2nd National Mental Health Plan proposed to expand procedural assistance services to 17 municipal governments, and efforts to legislate are actively being made. Therefore, this study tried to derive practical suggestions by in-depth analysis of the process of procedural assistance service. To this ends, interviews were conducted with 8 staff of one procedural assistance project group. As a result of the analysis, procedural assistance services were 'building trust as a process', 'providing information for users to understand', 'supporting decision-making based on the user's view', 'supporting institutional process', 'Supporting for taking initiative in treatment', 'Supporting for effective communication with family', 'Supporting for discharge through community alternatives', 'Advocates', and 'Practical constraints' were found. Through the analysis results, the core elements of procedural assistance services are 'supported decision-making', 'process', and 'communication'. Identifying the role of procedural assistance service, empowerment of assistants, expanding the role of peer supporter, promoting education of supported decision-making, protecting rights in the hospitalization process, improving human rights-based treatment environment, enacting and disseminating were suggested.