PURPOSE: To simplify a ladder and reduce its weight by connecting the side-part post member of an H-shaped panel member to the vertical side part of the H shape while the side-part post member is allowed to pivot freely for bending so that the side-part post member is demarcated as the post of the side part of the ladder when the side-part post member is spread to a use position.

CONSTITUTION: A ladder is composed of a crossbar member 4 for fixing a panel member, and a set of panels for a side-part post being provided at each end part. By the projection of the outside, upper, and lower edge parts of the panels 4, the panels 4 for the crossbar are connected one another, and at the same time are also connected to the panel for the side-part post while the panels can freely pivot. A projection 13 of the panel 4 is overlapped to a projection 17 of a panel 15. In the panel 15, a side-part post 2 of the ladder is demarcated with a side part 9 of the panel 4, and the panel 15 is formed by a body 18, the projection 17 at each of the side-edge parts, and projections 19 and 20 at an end part. Furthermore, the projections 19 and 20 are arranged in a zigzag, and the end parts are connected each other in the adjacent panels 15.