PURPOSE: To normally perform an ideal atomization of fuel and produce a uniform mixture gas, by controlling an irradiating energy of laser beams, transmitted through an optical fiber, in correspondence to a quantity of fuel jetted to provide an optimum value.

CONSTITUTION: Optical fibers 9aW9d are respectively disposed in the vicinity of fuel jetted from fuel jet valves 3aW3d respectively mounted to suction pipes 2aW 2d of a multicylinder internal-combustion engine 1, and this arrangement causes fuel, jetted by fuel jet valves 3aW3d to be irradiated with laser beams, generated from a laser beam oscillator 7, through a distributor 8 and optical fibers 9aW9d. An output energy and irradiating time of laser beams generated from the laser beam oscillator 7 are controlled into an optimum value according to an instruction from a controller 4, and this permits fuel to be efficiently radiated with sufficient energy to atomization of fuel.