PURPOSE: To decrease the diameter of a needle and to obtain a sharp transmitted image by forming the needle by using an image guide which is composed of a welded bundle of more than a specific number of quartz glass fibers and has an external diameter less than a specific value.

CONSTITUTION: The image guide 1 is a bundle of ≥1,000 quartz glass fibers 12; adjacent fibers are welded mutually and its external diameter is ≤1.0mm. When the number of quartz glass fibers is ≤100, picture elements are deficient and no sharp image is obtained. Further, when its external diameter is ≤1.0mm, it is too thick and not preferable. A light guide 8 guides illumination light and a light source 10 is provided at its free end. Then, the image guide 1 and light guide 8 are stored in a rigid tube 9 and an image ovservation system 11 is provided at the opposite end of the needle part to form the scope. Thus, the thin scope which provides a sharp transmitted image is obtained.