The article focuses on the problem of reorientation of the educational process of the primary school to ensure effective conditions for the development of critical thinking of schoolchildren. The necessity of comparing and generalizing the existing theory of critical thinking, defining the content of the essence "critical thinking" and its peculiarities has been proved. The essence of the concept "thinking" has been specified. It is revealed that one of its types is critical thinking. The significance of critical thinking in human life has been revealed. The necessity of using the method of content analysis for clarification of the concept "critical thinking" has been proved. According to the results of content analysis, the categorical features of this concept have been determined. The author's definition of the concept "critical thinking" has been proposed: scientific thinking, aimed at making the person's own decision by using intellectual and communicative techniques. It is revealed that critical thinking begins with the formulation of a problem (judgment) that needs to be solved; continues to search and comprehension of the information (arguments); construction of convincing argumentation; ends with making the decision (conclusion) as for the resolving of the issue. The structure of critical thinking has been defined: problem statement, information search, clear argumentation, decision making. The content of each structural component has been revealed and the role of a primary school teacher has been defined on each of them. The peculiarities of critical thinking of junior schoolchildren, such as: independence, analyticity, logic, sociality, have been determined. The idea is that the teacher should pay attention to the development of not only the pupils' intellectual and communicative techniques, but also personal qualities necessary for productive exchange of ideas: openness to the perception of other thoughts, tact, tolerance, and mobility. It is noted that the further scientific research requires the study of the purpose, content, methods and forms of development of critical thinking of junior schoolchildren.