A near-field light source device including a semiconductor laser comprised of laminated semiconductor layers and having a ring-type optical resonator with a plurality of wave guides connected via mirror portions, a light blocking film formed in one of the mirror portions and having a small opening not greater than a wavelength size, and a diffraction grating formed on the light blocking film. The light oscillated from the semiconductor laser is diffracted by the diffraction grating, the diffracted light is coupled to a rotation mode in the ring-type optical resonator, and near-field light is generated via the small opening.