Abstract: A liquid injection apparatus for lifting a maxillary sinus mucous membrane includes a passageway longitudinally extending through inside the apparatus; a connecting pipe formed at a rear portion to connect with a liquid supply apparatus; and an injection pipe 16 formed in a front portion, for being inserted into an implant hole extending to a bottom of a mucous membrane of a maxillary sinus, with a distal end of the injection pipe 16 spaced apart from the mucous membrane by a predetermined distance. The injection pipe is structured to inject liquid into the implant hole while closing the implant hole. The liquid injection apparatus can more easily lift the maxillary sinus mucous membrane without damaging the same by applying uniform pressure to the maxillary sinus mucous membrane when the maxillary sinus mucous membrane is being lifted.