The diploma thesis is focused on mathematical knowledge of pupils at the beginning of primary school. The theoretical part deals with characteristics of a preschool child and of a child at the beginning of a primary school, and especially with the specifics in their cognitive functions. Further the theses includes a chapter with an overview of several surveys about mathematical skills of Czech pupils. Finally, there is a chapter about building mathematical ideas at school and in a family. The practical part of the theses presents the results of the quantitative research in the field of mathematical ideas of a primary school child