A ridge type semiconductor optical device includes a first conductivity type semiconductor layer including at least a first stripe section; an active layer including at least an active stripe section on the first stripe section; a second conductivity type semiconductor layer including at least a second stripe section on the active stripe section; a ridge electrode on the second stripe section; an insulation film on an end face of each of the first stripe section, the active stripe section, and the second stripe section; and a film heater on the insulation film, the film heater overlapping with the end face of at least the first stripe section.