PURPOSE: To reduce the discharge of nitrogen oxides by pertinently executing sub-injection and main injection through a relatively simple structure to improve combustion in an engine.

CONSTITUTION: The first needle valve 31 is pressed against the first seat face 11c by a pressure spring 16, and pressure in a fuel reserving chamber 11b communicating with a feed hole 14 pushes up the first needle valve 31 against the elastic force of the spring. The second nozzle body 12 is provided above a free piston 17 vertically movably pressed against the upper end of the spring, and the second needle valve 32 in the second nozzle body 12 is provided so that it may be brought into contact with the second seat face 12b and separated from the face 12b by a laminated piezoelectric element 19. The second needle valve 32 opens and closes a fuel leading passage 12c to lead the fuel onto the upper face of the piston for discharging the fuel on the piston through fuel discharging passages 18b, 13c and an orifice 18d. A controller 33 controls the laminated piezoelectric element on the detected outputs of sensors 27, 28, 29.