Fabricated stair with double side beams

An assembly type stair with double side beams comprises a plurality of unit pedals, two inclined side beams arranged in parallel and a plurality of unit supporting plates arranged between the two inclined side beams. The multiple unit supporting plates are sequentially arranged in the length direction of the inclined side beam, and the heights of the multiple unit supporting plates are increased step by step; each unit supporting plate is provided with a supporting strip and two connecting parts in advance; the rear side and the front side of each unit pedal are connected to the supporting strip of the upper-stage unit supporting plate and the top of the lower-stage unit supporting plate respectively. Each unit supporting plate is vertically placed, and the two first bolts are vertically aligned, so that the bearing capacity of each unit supporting plate is enhanced, the middle of each unit supporting plate is not prone to deformation during bearing, and the structural strength of the stair is enhanced; and o