Tatami is peculiar to Japanese culture.
The existing oldest Tatami was made in Nara era (710-784). It has little bit different figure from Tatami which we expect now, it was called "Gosyo-no-Tatami 御床畳" made of 4-5sheets of Goza mat (Goza is a mat woven by herbaceous stem.) .
It was getting to be formed the figure known as Tatami in Heian-era (794-1185).