The present invention is a urea water injector relates to a module and the injector main body in which the injector is accommodated is mounted, a plurality having laminated structure on the outer surface of the body for injecting the urea water receives applying power from the outside to the exhaust gas purification of a vehicle assembly is installed in a lower portion of the rail to block the column end flange, and wherein the thermal barrier flange that is passed is disposed at the lower portion of the heat sink, the heat sink is formed with the refrigerant passage to urea water flowing therein from the lower side to the exhaust pipe It is configured to include a fixing portion bonded and fixed.