Foldable stairs embedded in a frame, in particular in a deep frame having increased wall height, comprising stairs segments movable with relation to each other, wherein the uppermost stairs segment is rotationally connected with the frame by means of a hinge mechanism, while the remaining stairs segments are positioned within said frame in the stairs closed state, wherein within the frame a movable step (4, 6) is positioned, pivotally connected to the internal surface of the wall of the frame, wherein the geometrical axis of the stringers of the uppermost segment of the stairs unfolded for use thereof, crosses the top surface of the stair tread (41, 62) of the movable step (4, 6) in the proximity of the centre of the tread (41, 62) width, characterized in that the uppermost stairs segment is attached to a cover that closes said frame at the bottom thereof in the stairs closed state, that the moveable step (4, 6) is supported by at least one supporting element connected with the cover, further characterised in that either (i) said supporting element of the movable step (4, 6) is the uppermost stairs segment, wherein the movable step is supported by hinged connectors coupling the uppermost stairs segment and preferably stringers of this segment with the movable step, wherein in the opened state of the stairs the hinged connectors are substantially aligned with the stringers of the uppermost stairs segment; or (ii) said supporting element of the movable step (4, 6) is the uppermost stairs segment, wherein the movable step is provided with supporting legs fixed to the tread of the step, wherein in the opened state of the stairs the supporting legs are substantially aligned with the stringers of the uppermost segment of the stairs and abut the frontal top surfaces of the stringers; or (iii) said supporting element of the movable step is at least one bracket attached to the cover, wherein the movable step is supported by hinged connectors coupling said at least one bracket attached to the cover with the movable step, wherein in the opened state of the stairs the hinged connectors are oriented in parallel to the stringers of the uppermost segment of the stairs. (i) said supporting element of the movable step (4, 6) is the uppermost stairs segment, wherein the movable step is supported by hinged connectors coupling the uppermost stairs segment and preferably stringers of this segment with the movable step, wherein in the opened state of the stairs the hinged connectors are substantially aligned with the stringers of the uppermost stairs segment; or (ii) said supporting element of the movable step (4, 6) is the uppermost stairs segment, wherein the movable step is provided with supporting legs fixed to the tread of the step, wherein in the opened state of the stairs the supporting legs are substantially aligned with the stringers of the uppermost segment of the stairs and abut the frontal top surfaces of the stringers; or (iii) said supporting element of the movable step is at least one bracket attached to the cover, wherein the movable step is supported by hinged connectors coupling said at least one bracket attached to the cover with the movable step, wherein in the opened state of the stairs the hinged connectors are oriented in parallel to the stringers of the uppermost segment of the stairs.