To provide a laser ignition device in which the ignition efficiency is improved and the laser pulse energy necessary for ignition is minimized by optimizing the pulse time width of laser. The laser ignition device includes: a pulse laser oscillator 1 configured to output a beam having a wavelength λ [μm] and a beam quality M2; an energy controller 2 configured to control energy of pulse laser outputted from the pulse laser oscillator 1; a lens 3 having a focal length f [mm] and configured to focus the pulse laser outputted from the pulse laser oscillator 1; and a pulse time width controller 14 configured to control a time width of the pulse laser, wherein the pulse time width controller 14 controls the time width of the pulse laser to be 0.6 to 2 ns.