This book provides the most comprehensive presentation of the basics of statistical physics. The book also features applications to quantum dynamics, thermodynamics, Ising model and statistical dynamics of free spins. The first part of the book explains the essence of statistical physics. It does this without going into details such as Liouville’s theorem or ergodic theorem, which are difficult for beginners and unnecessary for actual application of the statistical mechanics. In the second part, statistical mechanics ís applied to various systems which look different but have the same mathematical structure. In this way readers can deepen their understanding of statistical physics.