In a semiconductor light emitting element, a p-type layer (220), an active layer (230) and an n-type layer (240) are laminated on a substrate in this order. The n-type layer (240) is formed with a rectangular n-side electrode (241) whose width in one direction is equal to that of the n-type layer (240). The thickness t of the n-type layer (240) satisfies Formula 1 below. The semiconductor light emitting element includes a side surface (270) extending in the lamination direction and formed with a plurality of projections (271). Supposing that the wavelength of the light from the active-layer (230) is λ and the index of refraction of the n-type layer (240) or the p-type layer (220) is n, the average WA of widths at bottoms of the projections is set to satisfy WA≧λ/n. t ≥ ρ ⁢ ⁢ J 0 ⁢ e 4 ⁢ γκ B ⁢ T · W ⁡ ( L - W ) Formula ⁢ ⁢ 1 where L is width of the n-type layer in a direction different from the one direction, T is absolute temperature, W is width of the n-side electrode in a direction different from the one direction, J0 is current density at the contact portion between the n-side electrode and the n-type layer, e is elementary charge, γ is diode ideality factor, κB is Boltzmann constant, ρ is specific resistance of the n-type semiconductor layer.