|Cosmic neutrino is becoming a key probe for exploring the high energy universe. These neutrinos are expected to be produced by interactions of high energy hadronic (proton or nuclei) beams from cosmic accelerators with surrounding photons and/or matters. Because of its unique nature being undeflected in the galactic or extra-galactic magnetic fields and being transparent to the photon filled universe, cosmic neutrinos are expected to give direct information about the highest energy accelerators. IceCube is a cubic kilo-meter scale, deep-ice Cherenikov-light neutrino detector at the geographical South Pole. Detector construction was completed by the end of 2010. In this talk I will present the first results from the fully completed IceCube detector on searches for ultra-high energy neutrinos above PeV energy region, followed by future prospects.