A fastening device for sports shoes, provided with at least two flaps to be joined, including: a lever arm (404); a traction element (405) that is articulated, at one end, to the lever arm at a first axis; a base (409) that is associated with one of the flaps and from which vertical walls (410) protrudes for rotatably supporting the lever arm at a second axis; a rack associated with the other one of the flaps and can be detachably engaged by the other end of the traction element. The lever arm is constituted by a first element (412), which is articulated at one end to the vertical wall that protrudes from the base, and a second element (413), which is articulated to the opposite end of the first element at a third axis; the second element has a tab that protrudes beyond the third axis toward the vertical wall that protrudes from the base and interacts with the upper surface of the base during the rotation of the second element to open the lever arm.