To provide a flange installable in a required part of a toothed belt pulley, since the flange cannot be installed in an intermediate position of a toothed belt pulley body 3 in a conventional flange installing structure, though there is a case of requiring the flange in the intermediate position when winding a plurality of belts on one toothed belt pulley.

This flange can be fitted to an installation groove made in the required part of the flange of the toothed belt pulley body. Its cross-sectional shape is formed so that the inner diameter side of an addendum circle diameter of the toothed belt pulley body corresponds to the installation groove, and the outer diameter side is an installation groove width or more in the length of a base, and both side surfaces are set in the same as a conventional flange surface in both a dimension, a shape and accuracy. Its cross-sectional shape is made by circularly rounding a spring material by one-time winding.