This article is an essay for Introduction to the Sociology of Religious Conversion. As we know, the past few decades have witnessed dramatic growth in the religious conversion cases, since new religious movements have emerged in post Second World War. Today ''Sociology of Religious Conversion" is a sub-discipline, as a comprehensive research field in Sociology of Religion. In this paper, a brief explanation about the developments in this area will be given. And this, the phenomena of religious conversion will evaluate from the sociological perspective