PURPOSE: To provide a false-twister capable of easily selecting the optimal condition over a wide processing condition range (processing speed, fineness of the thread, etc.) and forming a high-quality uniform thread having physical properties stable to external disturbance (room temperature, variation of air flow in the moving of the thread, etc.).

CONSTITUTION: This false-twister is composed of a heater and a false-twisting apparatus placed at the downstream-side of the heater and enables the heat- setting of the twist applied to a thread and moving back along the thread. The characteristic of the false--twister comprises using a thread-temperature sensor 25 placed near the outlet of the heater to detect the temperature of the thread.