Who is the first rich man in world?

It's very difficult to tell because only fragments of history are recorded. You would imagine, however, that to be rich you would need to be part of a large civilisation or in a big city. The earliest proper city that we know about is Çatalhöyük which formed nearly 10,000 years ago.

The earliest figure in written history is Gilgamesh, king of the Uruk (which was where Iraq is now and notice the similarity sound-wise between Uruk and Iraq), who would certainly have been what we consider rich. However, there is a tradition in history of attributing stories about people in the past to people in the present (there's much evidence that the miracles of Jesus were long-known and had been previously attributed to others). Similarly with Gilgamesh, there is evidence of his story about the sacred bull in many civilisations and religions.

There is a reasonable chance that the man who was actually behind the story of Gilgamesh (not Gilgamesh himself) would have been the earliest "rich" man in history. Evidence of this story is found in (wait for it) Çatalhöyük.