Peter Shaffer is well-known for his brilliant successes in playwriting such as Five Finger Exercise and Equus. And his willingness to constantly revise his works is also well known. His masterpiece Amadeus went through at least six big revisions from its first version in 1979 to the one in 1998-9. In this paper, the three main versions of the script are compared with each other and Shaffer's changing attitudes to his idea of “the quest for God” are discussed. The focus of the discussion is set particularly on the climactic “Last Encounter” scene between Salieri and Mozart, which Shaffer reworked on again and again over a span of twenty years. It is also important to see the change of Salieri's characterization from a clever narrator in the first version to a tragic hero in deep agony in the last one. Through the revisions, the play has been transformed from a mono-drama like play into a great tragedy of human agony.