To prevent a lens barrel from tilting and easily manufacture a means therefor.

A lens barrel 10 is formed in a tubular support 11, holding an observation lens 3 and objective lenses 4, 5, 6. Around the intermediate position of the tubular support 11, a slit 12 is formed and a partition board 14 for positioning an optical member from the slit 12 is set in the support 11. An opening is made on the partition board 14. Since the portioning of the lenses 3-6 is performed by the partition board 14 around the central position of the support 11, tilting of the optical axis of the lenses can be prevented. Since the slit 12 can be formed from the outer periphery of the support 11 and the partition board 14 can be made separately from the support 11, it can be easily made.