To provide a thread rolling flat die which is easily detached from the fixing surface of a thread rolling machine after forming threads by rolling.

Grooves 21, 22 are respectively provided along the longitudinal direction of the die body 2 on the right side face 4 and the bottom surface of the thread rolling flat die 1. When fixing the thread rolling flat die 1 to the holder of the thread rolling machine, after respectively burying rubber tubes 35, 36 in the grooves 21, 22, the right side face 4 and the bottom surface are respectively made to closely contact with the two holding surfaces of the holder. After the threads are repeatedly formed by rolling with the thread rolling machine, when the thread rolling flat die 1 is adhered to the holder, compressed air is blown into the tubes 35, 36. Then, because the tubes 35, 36 are expanded by the feeding pressure of the compressed air, the right side face 4 and the bottom surface are forcibly separated. Then, the thread rolling flat die 1 can be readily detached from the holder.