To certainly thread a yarn sucked to a sucking member in a spinning part into a nip roller and a delivery roller composing a yarn feeding part and reduce piecing errors.

This piecing device is equipped with a threading member 21 for guiding the yarn Y sucked to the sucking member 13 in the spinning part from a free end 3a' of the nip roller 3a in the yarn feeding part to the vicinity to the center thereof in the piecing device of a spinning machine having a draft part 1, the spinning part 2 forming the yarn, the yarn feeding part 3, and taking-up parts 8, 9, 10 and 11 when ordered from the upstream side of the yarn.