PURPOSE: A coupling nut is provided to prevent parts from being wasted by effectively removing damaged coupling portions. CONSTITUTION: A coupling nut(100) is formed at an outer portion thereof with a female screw section(110). A screw hole(120) having a female screw section is formed at an inner portion of the coupling nut(100). Two holes(132) are formed at a front of the coupling nut in order to insert tools into the two holes(132). The coupling nut(100) is used for coupling a ceramic injector(220) to an aluminum body(210) of a distribution ring. The coupling nut(100) is inserted into a hole(212) formed in the aluminum body(210). The hole(212) is formed with a female screw section so that the coupling nut(100) is screw-coupled into the hole(212). In a state that the coupling nut(100) is coupled to the aluminum body(210), a bolt section(222) of the ceramic injector(220) is screw-coupled into the screw hole(120).
