Abstract from Wikipedia:
The Treaty of San Francisco, or San Francisco Peace Treaty, between the Allied Powers and Japan was officially signed by 49 nations on September 8, 1951 in San Francisco, California. It came into force on April 28, 1952. Although commonly known as the 'Treaty of San Francisco', its actual name is Treaty of Peace with Japan.
This treaty served officially to end World War II, to end formally Japan's position as an imperial power and to allocate compensation to Allied civilians and former prisoners of war who had suffered Japanese war crimes.
Neither the Nationalist Republic of China nor the Communist People's Republic of China were invited to the San Francisco Peace Conference and therefore neither signed this treaty. The Republic of China, however, enacted a separate Treaty of Taipei with Japan on April 28,1952 just hours before the Treaty of San Francisco went into effect, which acknowledged the terms of the San Francisco Treaty but added that all residents of Taiwan, the Pescadores were nationals of the Republic of China. Since the Treaty of Taipei did not come into force until August 5, 1952, almost 3 months after the San Francisco Peace Treaty came into force, whether the treaty of Taipei conclusively addresses the dispositon of Taiwan is disputed.