The money market has been existing in various forms for a long time. Until 1972, however, the market had supplied mainly short-term loans of commercial banks and loans of informal money lenders to business corporations. There was no market for notes and commercial papers of business corporations. Consequently, business corporations had to rely primarily upon commercial banks for short-term credit loans to supplement their working capital. The interest rate on loans of commercial banks had been set below a free market equilibrium rate and thereby, generated excess demands for the loans. Unsatisfied potential borrowers thus had to turn to informal money lenders for short-term cerdit loans of prohibitively high interest rate. Since 1972 investment and finance companies have been operating in the money market and their role in mobilizing short-term loans is increasing. This paper aims at estimating the equilibrium size of the money market.