An endoscope includes a head assembly having a first central axis for entry in a body cavity. In combination with the endoscope, a guide assembly includes a shaft sleeve having a lumen, for mounting on the head assembly therewith. An endless track device is supported around the shaft sleeve, for endlessly moving along the first central axis, for propulsion of the head assembly inside the body cavity. A support sleeve is disposed between the shaft sleeve and the endless track device, having a second central axis different from the first central axis, for supporting the endless track device movably. Preferably, the endoscope includes an imaging window area formed in a distal surface of the head assembly and offset from the first central axis. A position shift between the first and second central axes is predetermined according to a position shift between the imaging window area and the first central axis.
