An optical device comprising: a surface-emitting laser array having a plurality of light-emitting portions; a package member on which the surface-emitting laser array is disposed; and a transparent member retained on the package member and disposed on an optical path of a light beam emitted by the surface-emitting laser array, the transparent member including an incident plane on which the light beam emitted by the surface-emitting laser array is incident, each light-emitting portion amongst the plurality of light-emitting portions including a resonator comprising a lower semiconductor distributed Bragg reflector, a lower spacer layer, an active layer, an upper spacer layer and an upper semiconductor distributed Bragg reflector, wherein the incident plane of the transparent member is inclined with respect to an emitting surface of the surface-emitting laser array at a first inclination angle (Φ) which is smaller than a second inclination angle (Φ) at which the light emitted by one of the light-emitting portions is incident on another of the light-emitting portions via reflection by the transparent member, wherein the one and the other light emitting portions are spaced apart from each other by the greatest distance among the light emitting portions of the surface-emitting laser array, and characterised in that the first inclination angle of the transparent member is set such that for each of the light-emitting elements an incidence angle ψ of feedback light incident thereon is such that a reflectivity of the resonator at the incidence angle ψ is at least 99%, wherein the feedback light includes light emitted from any of the plurality of light-emitting portions within a beam spreading angle θ LD and reflected from the transparent member, where θ LD corresponds to 2σ or more, σ being the standard deviation, of a far-field pattern of the emitted light. a surface-emitting laser array having a plurality of light-emitting portions; a package member on which the surface-emitting laser array is disposed; and a transparent member retained on the package member and disposed on an optical path of a light beam emitted by the surface-emitting laser array, the transparent member including an incident plane on which the light beam emitted by the surface-emitting laser array is incident, each light-emitting portion amongst the plurality of light-emitting portions including a resonator comprising a lower semiconductor distributed Bragg reflector, a lower spacer layer, an active layer, an upper spacer layer and an upper semiconductor distributed Bragg reflector, wherein the incident plane of the transparent member is inclined with respect to an emitting surface of the surface-emitting laser array at a first inclination angle (Φ) which is smaller than a second inclination angle (Φ) at which the light emitted by one of the light-emitting portions is incident on another of the light-emitting portions via reflection by the transparent member, wherein the one and the other light emitting portions are spaced apart from each other by the greatest distance among the light emitting portions of the surface-emitting laser array, and characterised in that the first inclination angle of the transparent member is set such that for each of the light-emitting elements an incidence angle ψ of feedback light incident thereon is such that a reflectivity of the resonator at the incidence angle ψ is at least 99%, wherein the feedback light includes light emitted from any of the plurality of light-emitting portions within a beam spreading angle θ LD and reflected from the transparent member, where θ LD corresponds to 2σ or more, σ being the standard deviation, of a far-field pattern of the emitted light.