PURPOSE: To prevent damage and deformation of a belt, and wind up without loosening by reducing the tensile force to be applied to the belt when a winding diameter is small and a deadweight of the belt is small, and increasing the tensile force to be applied to the belt automatically in response to the increase of a winding diameter.

CONSTITUTION: A tensile force adjusting member 3 of a winding reel 2 has a support roller, a support rod and a tension roller 12, and the support roller is fitted to the upper end of the support rod freely to rotate, or is fixed to there. The tension roller 12 is fixed to the lower end of the support rod, and the support rod is fixed to a support member such as a base or the like, or is fitted to the support roller freely to rotate. Consequently, in the case that the support roller is fixed, the tension roller 12 is also fixed to a constant position, and in the case that the support rod is supported freely to rotate, the tension roller 12 can move pendulously. In the case that the support rod is fitted freely to rotate, the tension roller 12 is energized to the direction for touching a belt 8 by a spring.