A nitride semiconductor light emitting device includes a light emitting structure having n-type and p-type nitride semiconductor layers and an active layer formed therebetween. N-type and p-type electrodes are electrically connected to the n-type and p-type nitride semiconductors, respectively. An n-type ohmic contact layer is formed between the n-type nitride semiconductor layer and the n-type electrode and has a first layer of a material In and a second layer formed on the first layer and of a material containing W. The nitride semiconductor light emitting device has thermal stability and excellent electrical characteristics without heat treatment.