A yieldable restraint for the upper portion of the child seat for reducing the shock applied to the person sitting on the child seat by restraining equipment in case of a frontal crash. The restraint has an extensive energy-absorbing device in the member connected to the upper portion of the child seat by the tether belt. In case where a large turning force in the forward direction is applied to the child seat mounted on the seat and the connecting member is pulled forward by a force in excess of a prescribed value, the energy-absorbing device extends while absorbing a stress generated by the turning force. The energy-absorbing device may have a stress absorbing groove with crushable portions. Alternatively, a tear seam can be provided on the tether belt wherein the stress is absorbed by the tear seam being torn. Further, the tether belt can be woven so as to elongate while absorbing the stress.