PURPOSE: To detect a broken wire with high accuracy by logically processing both the detected signal of reflected light from a reflecting ring, which is provided so as to rotate coaxially with wire bodies and the rotation confirming signal of a rotary body, on detecting the broken wire of a wire body in an interwining machine.

CONSTITUTION: A reflecting ring 1 and a rotary body 8, which has hour bobbins 3 inside, are rotatably provided, both coaxially with respect to a piece of electric wire. Wire bodies 2, which are unwound from the bobbins 3 are introduced to the electric wire 7 through the twisting port 10 of the rotary body 8, and are interwined onto the electric wire 7 by means of the rotation of the rotary body 8. A photo-electric switch 4, which detects light, which is radiated onto, and reflected from, the reflecting ring 1, is provided near the outer surface of the ring 1, while detecting boards 6 as many as the wire bodies 2 are provided on the rotary body 8, and a rotary body detecting device 5 is provided in a position opposite to the detecting boards 6. The broken wire of the wire body 2 is detected from the outputs of the photoelectric switch 4 and the rotary body detecting device 5, and the interwining machine is immediately stopped when any broken wire is detected.