The book contains a consistent exposition of the foundations of quantum mechanics, including both non-relativistic and relativistic theory. In addition to the fundamental issues of quantum mechanics, it also deals with its various applications related to solid state theory, quantum radiation theory, etc. Considerable attention is paid to the analysis of precisely solved problems of quantum mechanics, such as harmonic oscillator, rotator, hydrogen atom. Some traditional issues are presented in the manual in a new way. Approximate methods of solving the Schrdinger equation are also given - the perturbation method and the quasiclassical method in KB and their applications (radiation theory, scattering theory, etc.). ).