The purposes of this book are as follows: 1) The occurrence of business cycle is closely connected with the essential features of a capitalist economy. The first aim of this book is to clarify this relationship. 2) To recount the history of business cycle in Japan and some other leading capitalist economies during the post war period. 3) To survey a variety of business cycle theories in both the Marxian and Orthodox economic traditions. 4) To construct a simple mathematical model and demonstrate the relationships between economic variables. We hope this helps readers to understand better the mechanisms of the business cycle. 5) To conduct a computer simulation of the model described above. Computer simulation is a powerful method both for examining the logical consistency of a theoretical model and exploring its conclusions.