This is a study on the effectiveness of the Korean government policy to convert non-regular workers to workers on non-fixed term contract in public sector, after 2017. This Korean government policy to convert non-regular workers to workers on non-fixed term contract was called the policy to convert non-regular workers to regular workers in public sector. As the result of being called this, it led to opposition from young people preparing for employment. By this study, it is tried to examine for the effect of the Korean government policy as to non-regular workers in public sector. Also, it is compared how much increases Korean trade union’s membership density by the related policy of Korean government, before and after 2017. But it cannot be proved how much the increased trade union’s membership density by non-fixed term workers in public sector has developed functions of benefit representation by trade union. That is the limit of this article.