Abstract: An inner rotor 5 has a recess 7 formed at a position corresponding to a navel 6 and the recess 7 has a taper surface 7a formed to the peripheral edge thereof. The end surface 6c of the navel 6 can be moved together with a support member 12 to an ordinary spinning position where it can be engaged with a thread Y drawn out through a thread guide and to a thread piecing position where it cannot be engaged therewith. When the thread is pieced, the navel 6 is disposed at the thread piecing position and after a seed thread is introduced into an outer rotor 2 from a thread drawing-out path 6b in the state that both the rotors 2, 5 are rotated, a fiber bundle in a fiber collecting portion 2a is drawn out together with the seed thread and a thread is spun without passing through the thread guide. Thereafter, the navel 6 is moved to the ordinary spinning position.