A laser ignition device capable of achieving stable ignition, preventing deterioration of a semiconductor laser element is provided, by suppressing the intensity of oscillated light leakage leaking towards semiconductor laser side from the laser resonator with a simple configuration. A laser ignition device 7 includes an excitation light source 1 emitting coherent excitation light LPMP, an optical element 2 transmitting excitation light LPMP, a laser resonator 3 oscillating oscillated light having high energy density by being irradiated with excitation light LPMP, and condensing means 6 condensing the oscillated light LPLS oscillated by the laser resonator 3. Moreover, the laser ignition device 7 is provided with a light-transmissive-reflective film 5 disposed between the excitation light source 1 and the laser resonator 3. The light-transmissive-reflective film 5 permeating the excitation light LPMP having short wavelength and reflecting oscillated light leakage LLEAK having long wavelength.