be suitable for non flexible endoscopes that is in the state that the attachment 1 is mounted to a non flexible endoscope body r of a cylindrical shape the side view observation optical system 2 on the attachment side 1 is aligned with the observation optical system o on the non flexible endoscope side and the bifurcated light incidence end surfaces 3a 3a which in the drawing are illustrated by one of them of the light guide member 3 on the attachment 1 side are aligned with the illumination optical systems respectively which are comprised of two fibers bundles b b in the drawings only one of them is shown on the non flexible endoscope side furthermore an illumination lens 4 having a diameter greater than that of the single light emitting end surface 3b is disposed at the light emitting end of the light guide member 3 which is integrated into a single member in this instant second embodiment also its function and effect are identical with those of the first embodiment and therefore the description thereof is omitted fig8 shows a third embodiment of the present invention this embodiment differs from the first embodiment in that the forward end portion of the attachment 1 is formed in a frusto conical shape and that the illumination lens 4 is so selected as to have a diameter identical with or somewhat larger than that of the light emitting end surface 3b of the light guide member 3 in compliance with the narrowing of the installment space the remainder of arrangement as well as the function and.