A method of producing a semiconductor optical device includes a first step of growing a stacked semiconductor layer including a first III-V group compound semiconductor layer for an active layer on a substrate; a second step of forming a silicon oxide film on the stacked semiconductor layer, the silicon oxide film having a predetermined film stress and a predetermined thickness; a third step of forming a strip-shaped groove in the silicon oxide film by etching the silicon oxide film, using a resist pattern formed on the silicon oxide film, until a surface of the stacked semiconductor layer is exposed; and a fourth step of growing a second III-V group compound semiconductor layer in the groove using the silicon oxide film as a selective mask.