PURPOSE: To provide an endoscope system which permits free attachment and detachment of rigid endoscopes of different image transmission types; a lens relay type and a fiber relay type, selectively to the same TV camera, permits free rotation of the TV camera relative to the rigid endoscope bodies and is capable of sufficiently removing the moires generated at this time.

CONSTITUTION: This endoscope observation system is so constituted that the rigid endoscope body 1 of the lens relay type having a relay lens 52 and the rigid endoscope 2 of the fiber relay type having an image guide 8 are freely attachable and detachable selectively to a photographing adapter 4 via their ocular parts 3, 3'. In addition, the rigid endoscope bodies and the TV camera 5 connected to the photographing adapter 4 are made freely rotatable relative to each other. Further, the ocular part 3' and the TV camera 5 are provided with optical low-pass filters in order to remove the moires of a CCD 7 in the TV camera 5.