A semiconductor light-emitting device includes a GaAs substrate; and an active layer provided over the GaAs substrate, the active layer including: a lower barrier layer lattice-matched to the GaAs substrate; a quantum dot provided on the lower barrier layer; a strain relaxation layer covering a side of the quantum dot; and an upper barrier layer contacting the top of the quantum dot, at least a portion of the upper barrier layer contacting the top of the quantum dot being lattice-matched to the GaAs substrate, and having a band gap larger than a band gap of the quantum dot and smaller than a band gap of GaAs.