A bobbin holder of a winder capable of preventing a variation in tension from occurring at the end parts and the center part thereof even if the length thereof is increased by an increase in the number of threads simultaneously wound thereon, comprising a tension member installed on the outer periphery of the holder having a tapered member with slopes on the outer peripheral surface and at both ends thereof for tensely installing the bobbin thereon, having the slope of a first sloped member fixed to the holder engaged with the slope at one end and having the slope of a second slope member coaxially slidable on the holder engaged with the slope at the other end and a compressive means pressing the second slope member in the axial direction of the bobbin holder to expand the tapered member in normal direction.
