The book is devoted to the systematic presentation of the foundations of quantum mechanics, t. e. Theory of motion of atomic particles . The first part of the book describes the non-relativistic quantum mechanics of Schrdinger, where, along with standard applications (harmonic oscillator, rotator, hydrogen atom, and t. d. Other applications of quantum theory, such as solid state theory, dispersion theory, etc., are also considered. d. The second part deals with the theory of Dirac, which allows to take into account not only relativistic, but also spin effects, as well as the theory of multielectron atoms and simple molecules. Finally, the third part is devoted to some general issues of the theory of the atomic nucleus and elementary particles, as well as some provisions of the secondary quantization method, which is a further development of quantum mechanics. The exposition is constructed in such a way as to help the reader to understand not only the physical foundations, but also to master the mathematical apparatus of quantum mechanics. The book can be used as a teaching tool for students of physical specialties of universities, pedagogical institutes and other universities, as well as for those who want to independently study quantum mechanics.