Each concept has its own extent and content. The content of the concept is determined by the definition, and the extent of the concept is determined by the method of division. In mathematics, concepts are most often formed with the help of definitions, which is not appropriate for early education. Concept forming is a complex process by which abstract concepts are arrived at by observing specific objects, and it includes scientific methods of analysis, synthesis, abstraction, and generalization. The aim of this thesis was to analyse how concepts are formed in school textbooks and whether the textbooks follow the Mathematics Curriculum, the basic document for teaching Mathematics in school. In addition to the curriculum, the textbooks were compared with the recommendations of mathematics education research literature. The forming of concepts was analysed on examples of the forming of the concepts of natural numbers up to ten, the forming of the concepts of multiplication and division, and on the example of the forming of the concept of a triangle. Based on the analysis, it was determined that the textbooks follow the procedures suggested by the literature, as well as that the curriculum requirements are respected. Textbooks greatly help teachers in planning and conducting lessons, but it is still teachers who are the key factor in the teaching process and give students what textbooks cannot offer.