Works that advocate site-specific theater are highly active in the recent Korean theater scene. Site-specific theater focuses on the historical, political and socio-cultural context of the location in which the performance is held and it shows interest in the ``now-present`` life that is conducted on a daily basis at the corresponding location, as well as issues on the features and identities of the community it is under. Therefore, site-specific theater sometimes shows socio-political criticism and participation, and sometimes act as critical commentary work for theaters in the existing system, while at other times, it is a formative experiment outside of the realm of traditional theatrical practices. But compared to such active practices, there is a relative lack of theoretical and critical work on site-specific theater. The reason why theoretical research is needed in Korea``s site-specific theater is because declarations by theater practitioners and producers or superficial newness alone cannot define it. This is because what may superficially look new may just be a rediscovery of forgotten theater or long traditions from a performing artist or theater history context. In particular, the challenge of performing arts against system and genre practices, socio-cultural criticism, political progressiveness, and dissolution of borders of life and theater that are represented in such work is similar to the 1960s theater experiments and particularly environmental theatre. Therefore, in order to accurately identify the meaning of site-specific theater, it is necessary to compare with environmental theatre and street theatre, which are previous works with similar mottos and formats. As site-specific theaters have been actively underway, there were also records and criticisms on individual theater. Critics first put attention on ``new expansion of space`` and ``active participation of audience`` among such work. But these are not features unique only to site-specific theater. What we must first pay attention to is not ``space`` but ``place`` that is the starting point of site-specific theater, and the meaning of ``placeness`` in performing arts. In site-specific theater, ``site`` is not just simply a space or environment. In site-specific theater, ``placeness``, or the uniqueness and exclusiveness of place and historical and social features of the site, are preemptive over all else and the contents and format of works also result from this. In site-specific theater, site is ``format`` and ``contents``, and the place itself is the ``storyteller``. Therefore, in order to properly understand the meaning of site-specific theater, which has rapidly been spreading in the performing arts world in the 21st century, we must examine the meaning of ``site`` in relation to medium-specificity of theater, which is both a site art and performing art. This study examines the meaning of site-specific theaters that have been performed recently in Korean theater focusing on issues of ``site`` and ``placeness``. For this, the concepts of ``space``, ``place`` and ``site`` must be arranged first. After examining the concepts discussed in a broad range in philosophical, sociological and geographic fields, their implications in the performing arts field will be examined. Also, the meaning of site-specificity in other art sectors will be summed up focusing on the arts sector that first practiced site-specific arts. Second, environmental theatre and street theatre that shows similar formative experiments with site-specific theater will be comparatively studied. Third, based on this, the question on what site is in today``s site-specific theater will be discussed focusing on Korea``s site-specific theater that has been showing progress through urban experience and personal experience projects. Through such studies, the features of site-specific theater that has becoming another trend in Korean theater in the 21st century, its contemporaneous meaning, and theater historical meaning will be put into order.