To provide a winding device capable of assisting rotation of a spindle rotor in accordance with increase/decrease of output torque of a winding device.

Provided is a winding device 1 for winding an electrode sheet 3 (belt-liked member) onto a winding core 2, which is equipped with: a driver 11 having a drive pulley 10 (drive rotor); a spindle pulley 20 (spindle rotor) being an axial cross-sectional shape similar to an axial cross-sectional shape of the winding core 2; two guide rollers 31, 32 arranged between the drive pulley 10 and the spindle pulley 20; and a driving belt 50 (annular member) stretched over the drive pulley 10 and the spindle pulley 20, in which the spindle pulley 20 and the winding core 2 rotate in an interlocked manner, a width L1 of two trajectories 51, 52 of the driving belt 50 between both guide rollers 31, 32 and the spindle pulley 20 is a width L2 in a short-length direction of the axial cross-sectional shape of the spindle pulley 20 or less, and lengths L4 of the two trajectories 51, 52 are the same.