A ladder includes a rung, two front legs and two rear legs, the front portions at the two sides of the rung are respectively hinged to the two front legs, wherein a hinged connection element comprises a connecting rod and two connection pieces, two connecting pieces are symmetrically attached to the two ends of the connecting rod, each connecting piece comprises a hinged portion, a pivot portion and a fixation portion, the fixation portion is connected to the connecting rod, the hinged portion is hinged to the central portion of the side edge of the rung and to the rear leg, the connecting rod is supported on the bottom of the rung when the rung is unfolded. The connecting piece is hinged to the rung and the rear leg. The fixation portion is fixedly connected to the connecting rod, the connecting rod rotates when the rung is unfolded or folded.