A semiconductor optical amplification device is disclosed that has a gain spectrum of a wide bandwidth. The semiconductor optical amplification device includes an InP substrate and an active layer on the InP substrate. The active layer has a quantum well structure formed by alternately stacking a barrier layer and a well layer, the barrier layer is formed from a tensile-strained InGaAs film, and the well layer is formed from a compressively-strained InGaAs film.