The objective of this course is for students to acquire a fundamental and practical understanding of the electrochemical equilibria and reactions in and on solids involving point defects in terms of the electrochemical potential. Topics include phase equilibria between electrons and ions, transport of electrons and ions as fundamentals; contact phenomena, topochemical reactions, transport through solid galvanic cell as applications; current research activities concerned. This course deals with the subjects from both microscopic and macroscopic viewpoints. Topics also include: basic concepts of the electrochemical system, defect structure of solids (metals, semiconducting materials), examples for the defect structure of solids, thermodynamic quantities of quasi-free electrons and defect electrons in semiconducting materials, Galvani and Volta potentials, Example for the defect structure of electrons and defect electrons, diffusion / migration of ions and electrons, application of solid Galvanic cell, and electrochemical solid state reaction.