A toe-piece of a ski binding for ski mountaineering has a base, a first jaw, a second jaw, an activating lever, a joint, a housing, and elastic means. The first jaw is provided with a first guide, and the second jaw is provided with a second guide. The activating lever is rotatably coupled to the base. The joint is activatable by the activating lever, which includes a first sliding element slidably coupled with the first guide and a second sliding element slidably coupled with the second guide, so that the activation of the activating lever causes, via the joint, the rotation of the first jaw and the second jaw. The housing is borne by the base. The elastic means are arranged in the housing so as to push the joint to wedge against the first jaw and the second jaw.