Provided are a flip-chip nitride-based light emitting device having an n-type clad layer, an active layer and a p-type clad layer sequentially stacked thereon, comprising a reflective layer formed on the p-type clad layer and at least one transparent conductive thin film layer made up of transparent conductive materials capable of inhibiting diffusion of materials constituting the reflective layer, interposed between the p-type clad layer and reflective layer; and a process for preparing the same. In accordance with the flip-chip nitride-based light emitting device of the present invention and a process for preparing the same, there are provided advantages such as improved ohmic contact properties with the p-type clad layer, leading to increased wire bonding efficiency and yield upon packaging the light emitting device, capability to improve luminous efficiency and life span of the device due to low specific contact resistance and excellent current-voltage properties.