Japan has experienced a prolonged stagnation since bursting the asset market bubble early in the 1990's. It is very important to understand the underlying problems in order to find a remedy to escape this stagnation. This thesis aims to theoretically analyse the current Japanese economy, especially from the viewpoint of multiple equilibria. According to this view, the same fundamentals can yield a multiple outcome depending on history or expectations. This thesis argues that Japan's situation can be regarded as a bad equilibrium which has been provoked by wide-spread pessimism and a bubble collapse. Three chapters independently attempt to construct theoretical models describing the current Japanese situation. Chapter 2 demonstrates that demand externalities yield multiple equilibria. In a bad equilibrium, firms dare not participate in trade, which causes aggregate demand and welfare to decrease. A global games approach then illustrates how equilibrium is selected. Chapter 3, with the objective of seeing if Japan's depression was provoked by the misconduct of monetary policy, investigates the relation between indeterminacy and a monetary policy rule using a sticky price and firm-specific investment model. The standard Taylor principle is shown to be almost sufficient to eliminate indeterminacy, which suggests that the Bank of Japan did not exacerbate the economy while interest rate rules functioned, that is, until 1999. Chapter 4 focuses on a zero nominal interest rate bound, which has been observed since 1999. The ineffectiveness of the monetary policy yields a bad short-run outcome where real economic activity and asset prices become lower. There are long-run multiple equilibria in this story, and that is our explanation for the problem. Within this model, however, our .analysis does not justify a claim that a zero bound for the interest rate causes a long-run equilibrium to be a bad one.