Despite a rich research done abroad which has confirmed a strong influence of self-efficacy on performance and attitudes in relation to mathematics, there has been paid little attention to this concept in the Czech Republic. This article introduces the concept of self-efficacy and domain-specific self-efficacy in mathematics while also presents realized research with two main goals: 1) to develop and verify a Czech scale of mathematical self-efficacy for primary and secondary schools 2) to find out the relationship between mathematical self-efficacy and performance in mathematics. In the research group, there were 436 boys and girls from fourth and eighth grades. They completed a scale of mathematical self-efficacy, a mathematical questionnaire and a mathematical test with tasks provided by TIMSS 2007 project. The final Czech scale of mathematical self-efficacy consist of 30 items with a five-point evaluation scale and reports high reliability (Cronbach’s alpha = 0,9). Mathematical self efficacy significantly correlated with performance in the mathematical test. There was also a significant difference in the level of self-efficacy between younger and older children.