Abstract: A mouthpiece for an endoscope includes a main body disposed to closely contact an outer side of a mouth and provided with an central insertion hole through which the endoscope is inserted, an guide body supported on the central insertion hole of the main body to guide insertion of the endoscope, and a movement preventing unit disposed in an oral cavity to prevent the mouthpiece from moving in the oral cavity. The guide body and the movement preventing unit may designed to be separable from the main body.