A closure device, particularly usable in ski boots composed of a shell with which a front quarter and a rear quarter are associated, includes a lever which is pivoted, at one end, to the rear quarter or to a slider which is slidable at an adapted guide to which an adjustable-length rod is pivoted in an intermediate region. The rod interacts, at its free end, with a locking element which is located at the rear quarter or on the slider. A first traction element rigidly associated with the shell and at least one second traction element, which is coupled, at its ends, to a member in relative motion with respect to the pivoting axis of said lever and/or to a member which is fixed with respect to the pivoting axis, are furthermore associated with the slider. The device furthermore includes elements adapted to limit the opening angle between the lever and the rod as well as a resilient member adapted to keep the free end of the rod in contact with the locking element.