To provide a bobbin for an optical fiber winding the optical fiber by a conventional winding tension and allowing accurate measurement of a PMD value, and an accurate measuring method for the PMD value of the optical fiber wound on the bobbin.

A predetermined amount of the optical fiber 1 is wound on the bobbin for storage or delivery to a user. When measuring the PMD value of the optical fiber 1, a part of a winding leading end or a part of a winding trailing end of the optical fiber 1 is wound on a separator part 6 provided next to a bobbin body part 2 winding the optical fiber 1 and capable of reducing a circumference of a winding drum part 8, the circumference of the winding drum part 8 of the separator part 6 is reduced, and the PMD value of only the optical fiber 1a wound on the separator part 6 is measured.