To provide a yarn winder capable of certainly preventing wasteful cutting of yarn immediately after the start of the yarn taking-up following the completion of the doffing operation and suppressing a drop of the working efficiency.

The yarn winder 1 is equipped with: a plurality of takeup units 2 to pull up a yarn from a supplying yarn package 5 onto a takeup tube 7 so that a takeup package 6 is formed; and a doffing device 3 to remove the package 6, set a new takeup tube 7, and fix thereto a yarn end, and further the arrangement includes a unit controller 41 to control the motions of the takeup units 2, a yarn diameter sensor 19 installed on a yarn guide leading from the supplying package 5 to the takeup package 6, and a clearer controller 60 equipped with a zero-point adjusting function for the diameter sensor 19, wherein the unit controller 41 transmits the zero-point correction signal to the clearer controller 60 while the doffing device 3 is in the doffing operation.