To provide a stair and a construction method for the stair at a low manufacturing cost, performing unitization abounding in practicality required in construction, and abounding in practicality at a construction site.

The stair 1 includes a tread 2 forming each stage and a decorative plate 3 covering the surface of the tread 2. The stair 1 is so constituted that the decorative plate 3 is slid along the surface of the tread 2 to mount the decorative plate 3 when the decorative plate 3 is mounted. A bending section 4 (10) stopping the slide of the decorative plate 3 at the fixed position of the tread 2 is provided to the edge section 3b of the decorative plate 3.