A heel piece for an alpine ski attachment comprises a base element (1), fastenable to a ski (S), an upper element (2), coupled to the base element (1), and a pair of rotatable arms for hooking to a shaped portion exhibited in a rear part of an alpine ski boot. A pair of pins (32) borne by the arms (31) project from the upper element (2). An elastic element (4) maintains the pins (32) at a predetermined reciprocal distance. The elastic element is stressed by a separation of the pair of pins (32), determined by a lowering of the ski boot onto the ski and by insertion between the pins (32) of the shaped portion. The pins (32), following complete insertion of the shaped portion between the pins, lock against an upper part of the shaped portion to hook the ski boot.