An active layer having a type 2 multi-quantum well structure includes a plurality of pair thickness groups having different thicknesses, including a first pair thickness group and a second pair thickness group. The first pair thickness group g1 includes 10 to 100 pairs, each monolayer of the pairs having a thickness of 1.5 nm or more and less than 3.5 nm. The second pair thickness group g2 includes 10 to 100 pairs, each monolayer of the pairs having a thickness of the minimum thickness (a second group minimum thickness) or more and 7 nm or less, the minimum thickness being larger than the maximum monolayer thickness 3.5 nm of the first pair thickness group.