A laser source device includes a laser source for oscillating a laser beam with a predetermined wavelength, a mirror for reflecting the laser beam emitted from the laser source to form a resonator, and including a dielectric multilayer film having a property of reflecting a light beam with an oscillation wavelength and transmitting a light beam with a conversion wavelength, a wavelength conversion element disposed between the laser source and the mirror for converting the laser beam with the oscillation wavelength emitted- from the laser source and emitting a laser beam with the conversion wavelength, and a bandpass filter disposed between the laser source and the mirror, and including a bandpass filter multilayer film having a bandpass property at least around the oscillation wavelength.