This book aims to describe the physics of the integer and fractional quantum Hall effects (QHE) from a theoretical side. In the classical Hall effect, the Hall resistance is proportional to the applied magnetic field strength and varies continuously. So, the discovery of a stepwise change of the Hall resistance by von Klitzing in an ultra-thin layer of a MOSFET was a big surprise. The QHE is a macroscopic phenomenon and shows the exact quantum structure, which is one of the most fundamental phenomena in physics. The fractional quantum Hall effect has been explained assuming quasi-particles with fractional charges or Jain's composite fermions, the existence of which has not been verified experimentally. The author has been developing a theory based on a standard treatment of an interacting electron system without assuming any quasi-particle. This book will be easily understood by undergraduate students in physics. Knowledge of quantum field theory is needed to study Chapter 9.