  We study the final state of the gravitational collapse of uniformly rotating
supramassive neutron stars by axisymmetric simulations in full general
relativity. The rotating stars provided as the initial condition are marginally
stable against quasiradial gravitational collapse and its equatorial radius
rotates with the Kepler velocity (i.e., the star is at the mass-shedding
limit). To model the neutron stars, we adopt the polytropic equations of state
for a wide range of the polytropic index as $n=2/3$, 4/5, 1, 3/2 and 2. We
follow the formation and evolution of the black holes, and show that
irrespective of the value of $n (2/3\leq n \leq 2)$, the final state is a Kerr
black hole and the disk mass is very small ($< 10^{-3}$ of the initial stellar
mass).
