In a light source device, a light-emitting element and a coupling lens configured to condense a beam of light emitted from the light-emitting element are held by a holding member. The holding member has an adherend that is opposite to a surface of the coupling lens facing to the light-emitting element in a direction of an optical axis of the coupling lens. Part of the surface of the coupling lens facing to the light-emitting element is bonded to the adherend of the holding member. In the optical scanner which includes this light source device, a beam of light emitted from the light source device is deflected by a deflector so that a target surface is scanned with the beam of light, and the deflected beam of light is caused by an image forming optical system to focus on the target surface, to form an image thereon.