According to one embodiment, a semiconductor light emitting device includes an n-type semiconductor layer, a p-type semiconductor layer, and a light emitting layer. The p-type semiconductor layer includes a first p-side layer, a second p-side layer, and a third p-side layer. A concentration profile of Mg of a p-side region includes a first portion, a second portion, a third portion, a fourth portion, a fifth portion, a sixth portion and a seventh portion. The p-side region includes the light emitting layer, the second p-side layer, and the third p-side layer. A Mg concentration of the sixth portion is not less than 1×1020 cm−3 and not more than 3×1020 cm−3. The Al concentration is 1/100 of the maximum value at a second position. A Mg concentration at the second position is not less than 2×1018 cm−3.