At the end of the Japanese colonial era, Taiwan's money supply had increased tremendously. Due to price regulation, inflation remained relatively minor, however. Beginning in 1946, money supply increased gigantically, and inflation became a serious problem. This study shows that in the first stage of Taiwan's hyperinflation, money supply increase was the result of Bank of Taiwan's loans to the public enterprises. In the later stage, financing government budget deficit became the main cause of money supply increase. A monetary reform program was initialized in June 1949. Unfortunately, the Nationalist government retreated to Taiwan at the end of 1949, government budget deficit became even more severe than before, and exerted more pressure on prices. The Korean War broke out on June 25, 1950, and U.S. aid to Taiwan was resumed immediately. The U.S. aid enabled the Nationalist government to reduce the budget deficit, and eventually ended the hyperinflation.