PURPOSE: To easily construct even when an error occurs during construction of a building and to perform regulation of height by a method wherein a spanning fitment between the upper ends of upper and lower girders and the upper part of a stair floor are rendered eccentrically rotationally, in a stair device to form a link mechanism having sides situated in parallel.

CONSTITUTION: One set of ascendant girders consist of two of upper and lower girders 1 and 2 paralleling in a side oblique state. Treads 15 and 15A in a plurality of stages horizontally span between the upper and lower girders 1 and 2 on the left and right sides and the ends on both sides thereof are pivotally arranged, and a link mechanism having sides paralleling each other consists of the upper and lower girders 1 and 2 and the treads 15 and 15A. In a spanning fitment H for the upper ends thereof and a stair floor upper part U, axes 11 and 12 of the upper end parts of the upper girder 1 and 2 and the lower girder 2 form an eccentric axis. Thus, even when en error in a vertical distance between the floor upper part U and a floor lower part D spanning in a hooked state occurs, by eccentrically rotating the eccentric axes 11 and 12, the treads 15 and 15A are always kept in a horizontal state.