A light-emitting gallium nitride-based III-V group compound semiconductor device and a manufacturing method thereof are disclosed. The light emitting device includes a substrate, a n-type semiconductor layer over the substrate, an active layer over the n-type semiconductor layer, a p-type semiconductor layer over the active layer, a conductive layer over the p-type semiconductor layer, a first electrode disposed on the conductive layer and a second electrode arranged on exposed part of the n-type semiconductor layer. A resistant reflective layer or a contact window is disposed on the p-type semiconductor layer, corresponding to the first electrode so that current passes beside the resistant reflective layer or by the contact window to the active layer for generating light. When the light is transmitted to the conductive layer for being emitted, it is not absorbed or shielded by the first electrode. Thus the current is distributed efficiently over the conductive layer. Therefore, both LED brightness and efficiency are improved. Moreover, adhesion between the conductive layer and the p-type semiconductor layer is improved so that metal peel-off problem during manufacturing processes can be improved.