PURPOSE: To enable a fiberscope to be oscillated while a position to be observed is observed, by forming a recessed groove in a knob member to receive a sliding mover piece in the recessed groove so that the proximal end of an oscillating wire fixed on the distal end to the end of a fiber body is latched by the mover piece.

CONSTITUTION: An illuminating light is radiated through a light guide to a position to be observed to transmit a reflected image to an eyepiece for observation by the naked eye, camera or the like. When a mover piece 13 is received in a recessed groove 12, an irregular tooth 27 is screwed in a screw portion 24 of an operating link 11 and the operating link 11 is rotated in the directions of arrows A, B. Then, the mover piece 13 is screwed forward and backward along the screw portion 24 in the directions of arrows C, D. An oscillating wire 5 is inserted into a small diameter tube 1 of an optical fiber body 4 so that the proximal end 29 is latched by the mover piece 13 and the distal end 30 is fixed to the distal end 6 of optical fiber body 4. An end tube 1a of tube body 1 is swung about a tube 31 fixing portion 33 as shown by the arrow so that the end 6 of optical fiber body 1 is oscillated. When the mover piece 13 is slid in the direction of arrow D, the tension of wire 5 is released and returned to the linear form.