An object is to provide a nitride-based semiconductor light emitting device capable of preventing a Schottky barrier from being formed at an interface between a contact layer and an electrode. LD1 is provided as a nitride-based semiconductor light emitting device provided with a GaN substrate 3, a hexagonal GaN-based semiconductor region 5 provided on a primary surface S1 of the GaN substrate 3 and including a light emitting layer 11, and a p-electrode 21 provided on the GaN-based semiconductor region 5 and comprised of metal. The GaN-based semiconductor region 5 includes a contact layer 17 involving strain, the contact layer 17 is in contact with the p-electrode, the primary surface S1 extends along a reference plane S5 inclined at a predetermined inclination angle [theta] from a plane perpendicular to the c-axis direction of the GaN substrate 3, and the inclination angle [theta] is either in the range of more than 40 DEG and less than 90 DEG or in the range of not less than 150 DEGand less than 180 DEG. The GaN-based semiconductor region 5 is lattice-matched with the GaN substrate 3.