Despite that the public's need for non-medical psychological counseling services has been increasing, various social problems are occurring due to the absence of a public management and supervision system for psychological counselor qualifications. To tackle this problem, we attempted to derive the optimal legislative alternative through an ex-ante assessment of five bills related to the national qualification of psycholo-gical counseling submitted to the 21st National Assembly. An ex-ante assessment is conducted based on its definition and main procedures, involving three criteria: (1) ‘relevance’, which examines the necessity of legislation and the possibility of achieving the legislative purpose, (2) ‘consistency’, which examines the internal consistency of the legislation and its adhesion with other laws, and (3) ‘sustainability’, which examines acceptability of the legislation. Our study derived an optimal integrated legislative plan for a stable and sustainable system for qualified psychological counselors. We suggested that the professionalization of psychological counseling through legislation should be carried out in a way that prioritizes public interest, such as improving the mental health of the people, minimizing service gaps, and granting exclusive rights to psychological counselors with expertise and capabilities.