PURPOSE: To provide the subject separator for seaming machines that are arranged in opposition to the heads of movable hooks at a specific interval, equipped with a plurality of piercing needles that can successively seize and separate threads held in an array from the top in order and is suitable for seizing yarns having a variety of diameters.

CONSTITUTION: The piercing needles 20 are arranged on the head of the hook 16 that is set in the frame 10 of the separator in which the separation stroke moves along the guide so that they may be parted by the distance of about 3/4-1/2 diameter of the yarn to be separated. When the frame advances toward the top yarn 14a of the yarn array to be separated, one of the piercing needles 20 pierce the threads to the head of the thread 14a to seize it, for example, at the lower end in the gap 12, and the other pierce needles pierce the following threads 14b on the lower position than the thread 14a and hold it on the upper top of the gap 12 and the frame 10 is actuated to separate the seized thread from the other threads in the thread array. Thus, piercing needles 20 are provided to seize and separate the threads in turn from the top thread and the threads having different diameters can be accurately seized and separated regardless of its arrangement.