PURPOSE: To obtain a long-life optical fiber cable by measuring the sent-in quantity at one end of an optical fiber composite electric conductor and the drawn-out quantity at the other end of the optical fiber composite electric conductor, and nearly equalizing the sent-in quantity and drawn-out quantity to each other.

CONSTITUTION: When a new optical fiber cable 1 is sent in the optical fiber composite electric conductor, a sent-in quantity measuring instrument 2b measures the sent-in quantity L1 of the new optical fiber cable 1 and sends its signal to a comparison controller 4. A drawn-out quantity measuring instrument 3b measures the drawn-out quantity L2 of a drawn-out old optical fiber cable and sends its signal to the comparison controller 4. The comparison controller 4 compares those signals L1 and L2 with each other and sends a command for a speed increase to a sending-in speed controller 2a when L2>L1. Consequently, the residual tensile force applied to the optical fiber cable is reduced to obtain the long-life optical fiber cable.