A device (10) for fixing a pulley (40) includes a rotating pin (12) on the outer surface of which the pulley (40) may be fixed. The rotating pin (12) has at least one locking element (50) movable between a first locking position where it retains the pulley (40) and a second releasing position where it does not retain it. The locking element (50) is coupled with at least one element (60) which can be operated by the user so that the displacement of said at least one element (60) which can be operated by the user causes the displacement of the at least one locking element (50) between the first and second position.