According to one embodiment, a semiconductor light emitting device includes an n-type semiconductor layer, an electrode, a p-type semiconductor layer and a light emitting layer. The p-type semiconductor layer is provided between the n-type semiconductor layer and the electrode and includes a p-side contact layer contacting the electrode. The light emitting layer is provided between the n-type and the p-type semiconductor layers. The p-side contact layer includes a flat part having a plane perpendicular to a first direction from the n-type semiconductor layer toward the p-type semiconductor layer and multiple protruding parts protruding from the flat part toward the electrode. A height of the multiple protruding parts along the first direction is smaller than one-fourth of a dominant wavelength of light emitted from the light emitting layer. A density of the multiple protruding parts in the plane is 5×107/cm2 or more and 2×108/cm2 or less.