To provide a structurally simple triple ladder which can decrease costs.

A front wall 13a of a support of an intermediate ladder 2 is superposed on the front side of a back wall 11b of a support of a front ladder 1 in a longitudinally slidable manner, so that the intermediate ladder 2 can be expanded/contracted with respect to the front ladder 1. A front wall 15a of a support of a back ladder 3 is superposed on the backside of the back wall 13b of the support of the intermediate ladder 2 in such a manner as to be relatively movable in a longitudinal direction, and they are connected together in such a manner as to be relatively slidable via a connecting member 5, so that the back ladder 3 can be expanded/contracted with respect to intermediate ladder 2.