PURPOSE: To make it possible to adjust the surplus length of an optical fiber cable in both right and left directions.

CONSTITUTION: This surplus length treating device has a reel 1 for the optical fiber cable on a right direction side, a reel 2 for the optical fiber cable on a left direction side and cylindrical parts 3 playing the role of bridging the optical fiber cable between the right direction reel 1 and the left direction reel 2. The adjustment of the surplus length of the optical fiber cable on the right direction side is executed by rotating the reel l on the right direction side. The adjustment of the surplus length of the optical fiber cable on the left direction side is executed by rotating the reel 2 on the left direction side.