PURPOSE: To save labor and smooth operation by automatically measuring the amount of a resin in stopping feed of the resin to a resin coating vessel in changing over an optical fiber perform and automatically cutting an optical fiber bare wire after the passage of a prescribed time from the aforementioned stop of the feed.

CONSTITUTION: A cutting device for an optical fiber bare wire is provided between a spinning furnace 1 for the optical fiber and a resin coating vessel 8 located thereunder and the amount of the resin in the vessel 8 in stopping the feed of the resin to the coating vessel 8 is measured with an automatic measuring device. After the passage of a prescribed time from the stop of the resin feed to the coating vessel 8, the above- mentioned cutting device for the optical fiber bare wire is operated by an automatic controller. For example, a type of cutter, having rack gears 34 in a piston rod 33 of a pneumatic cylinder 30 and a pair of left and right cutters 36 and 37 subjected to rotating operation with pinions 40 meshing with the rack gears 34 and capable of cutting the optical fiber bare wire according to closing operation of the left and right cutters 36 and 37 can be used as the cutting device for the optical fiber bare wire.