There are provided a light source device and an endoscope system that can switch plural kinds of illumination light without a user's instruction.A light source unit (20) emits first illumination light that includes a first red-light wavelength range and is used to emphasize a first blood vessel and second illumination light that includes a second red-light wavelength range and is used to emphasize a second blood vessel different from the first blood vessel. A light source control unit (21) performs control to cause each of the first illumination light and the second illumination light to be emitted for a light emission period of at least two or more frames and to automatically switch the first illumination light and the second illumination light.
