A light source device includes a light source unit, a light condensing unit that includes a condenser lens which condenses light from the light source unit and a collimator which renders the condensed light into parallel light having a predetermined diameter, and a wavelength variable interference filter which emits light having a wavelength depending on a gap dimension of a pair of reflection films. The predetermined diameter is smaller than a size of a facing region of the wavelength variable interference filter where the pair of reflection films faces each other.
