Fabricated steel structure stair

The invention discloses a fabricated steel structure stair which is applied to be connected between the ground and building floor plates or applied to be connected between two adjacent building floor plates, and the steel structure stair comprises two steel side plates which are oppositely arranged at an interval; a ladder section main body is arranged between the two steel side plates and comprises a plurality of L-shaped steel supporting plates, and the L-shaped steel supporting plates are sequentially connected in the length direction of the steel side plates; the horizontally-arranged part of the L-shaped steel supporting plate is arranged to be a tread part, and the vertically-arranged part of the L-shaped steel supporting plate is arranged to be a kicking part. The tread portion of each L-shaped steel supporting plate is connected with the kicking portion of the adjacent L-shaped steel supporting plate located below the tread portion, and the top end face of the tread portion of each L-shaped steel supp