A propulsion assembly for mounting on a tip device of an endoscope includes a barrel sleeve having inner and outer surfaces. A flexible endless track device is disposed to extend along the inner and outer surfaces of the barrel sleeve, for endlessly moving in an axial direction, for propulsion by contacting a wall of a body cavity. A drive gear is engaged with the endless track device, for moving the same. A driving mechanism rotates the drive gear. Engaging teeth are formed on the endless track device at a predetermined pitch, arranged serially, moved by the drive gear in mesh therewith. A peripheral surface of the engaging teeth is curved without a sharp form. Furthermore, a support sleeve is disposed between the driving mechanism and the endless track device, for supporting the drive gear in a rotatable manner.
