The subject of this article is naive art, one of the important artistic trends of the XX - early XXI centuries. The object of the study is the main approaches of experts to the study of naive art. At the first stage: 1930s-1950s - a historical approach was formed, which is associated with the definition of naive art as one of the forms of amateur art, "hobby". At the second stage - the 1960s-1990s, the traditional approach is considered, which includes the consideration of naive art as a separate artistic direction. Innovative approach: 1990-2000: determined by the study of naive art from the point of view of outsider art. The main contribution of the research is to determine the criteria of naive art as a separate direction, and in the context of a whole range of directions of non-professional art. These include amateur creativity, naive art, "borderline artists", art brut, the art of outsiders. Their main features are determined. The novelty of the research is a generalizing analysis of the presented approaches to the study of naive art of the twentieth century, the main criteria of naive art are clarified and described. During its attribution and examination, it will allow the most accurate and complete to give an art criticism assessment, to talk about the authenticity, authorship, historical value of specific works of naive art.