A laser light source device may include a laser diode, first and second optical elements, a diffraction grating, and a detector. The first optical element may collimate laser light emitted from the laser diode. The diffraction grating may reflect zero-order light in the collimated laser light in a predetermined direction other than a direction toward the laser diode and may reflect first-order light in the collimated laser light toward the laser diode. The second optical element may reflect the zero-order light reflected by the diffraction grating in a predetermined direction while transmitting a part of the zero-order light reflected by the diffraction grating. The detector may detect at least one of a wavelength and an intensity of the light that passes through the second optical element.