A propulsion assembly for an endoscope includes a support sleeve and a barrel unit. An endless track device is disposed to extend along inner and outer surfaces of the barrel unit, for endlessly moving in an axial direction of an elongated tube of the endoscope, and contacting a wall of a body cavity, for propulsion of the elongated tube. Worm wheels are disposed on the support sleeve, for driving the endless track device by engagement therewith. Plural idler rollers are disposed on the inner surface of the barrel unit in a rotatable manner, for keeping the endless track device movable in driving of the worm wheels. An guide projection is formed on the endless track device. A guide groove is formed in the barrel unit, for receiving the guide projection, to guide the endless track device on the barrel unit in the axial direction.
