World society has developed diverse institutions for protecting human rights in the modern era. The International Labor Organization (ILO) is one of these international organizations, and deals with issues of human rights related to labor. Established in 1919 and now a expert body of the UN, the ILO supervises labor conditions of the countries that have ratified its conventions and recommendations. One of the most important conventions is the convention on forced labor, ILO Convention 29. The issue of military sexual slavery by japan was first addressed by the ILO in 1995 as clear violation of Convention 29. Using the primary materials of the NGOs and the labor unions, and the result of the participatory observations at the ILO meetings, this paper aims to clarify the nature of the ILO and the structure of problem raising and discussions at the ILO, by investigating the processes that the military sexual slavery issue has been rasied and discussed. I will explore the following processes: how the Korean and japanese NGOs transmitted the issue to the labor unions of Korea and japan, how the labor unions presented the issue to the Expert Committee, the Expert Committee’s judgment of the issue as a violation of the Convention 29, and the labor unions’ efforts to have this issue selected as a critical cases to be addressed at the general conference, etc.