A light source device includes plural light-emitting elements that emit lights, a wavelength selection element that has plural light selection areas in which wavelength selection is performed for the lights emitted from the plural light-emitting elements, respectively, and selectively reflects a part of the lights emitted from the plural light-emitting elements, a state detecting unit that detects states of the plural light selection areas of the wavelength selection element, and a state changing unit that changes, according to the states of the plural light selection areas detected by the state detecting unit, the states of the light selection areas of the wavelength selection element to make wavelengths of the lights selected in the plural light selection areas different from one another.