A nitride semiconductor element includes a sapphire substrate including: a main surface extending in a c-plane of the sapphire substrate, and a plurality of projections disposed at the main surface, the plurality of projections including at least one projection having an elongated shape in a plan view; and a nitride semiconductor layer disposed on the main surface of the sapphire substrate. The at least one projection has an outer edge extending in a longitudinal direction of the elongated shape, the outer edge extending in a direction oriented at an angle in a range of −10° to +10° with respect to an a-plane of the sapphire substrate in the plan view.