Stair scaffolding module for a modular stair scaffolding tower, comprising: - in each module corner area (24, 26, 28, 30) of the stair scaffolding module (M 1, M 2, M 3) formed with a quadrangular circumferential contour, a vertical post (32, 34, 36, 38) with an upper post end area and a lower post end area, - in the upper post end areas of the vertical posts (32, 34, 36, 38), an upper group (Go) of horizontal ledgers (60, 62, 64, 66) connected thereto, - in the lower post end areas of the vertical posts (32, 34, 36, 38) a lower group (Gu) of horizontal ledgers (52, 54, 56, 58) connected thereto, - a stair unit having an upper stair unit end area and a lower stair unit end area, wherein the upper stair unit end area is detachably connected to a horizontal ledger of the upper group (Go) of horizontal ledgers (60, 62, 64, 66) and the lower stair unit end area is detachably connected to a horizontal ledger of the lower group (Gu) of horizontal ledgers (52, 54, 56, 58), wherein the upper group (Go) of horizontal ledgers (60, 62, 64, 66) on one side of the quadrangular circumferential contour comprises a horizontal ledger for a detachable connection with the upper stair unit end area, and the lower group (Gu) of horizontal ledgers (52, 54, 56, 58) on another side of the quadrangular circumferential contour opposite said one side of the quadrangular circumferential contour comprises a horizontal ledger for a detachable connection with the lower stair unit end area, characterised in that the upper group (Go) of horizontal ledgers (60, 62, 64, 66) comprises in association to all sides of the quadrangular circumferential contour, one respective horizontal ledger (60, 62, 64, 66) detachably connected to two of the vertical posts (32, 34, 36, 38) provided in the four module corner areas (24, 26, 28, 30), in that the lower group (Gu) of horizontal ledgers (52, 54, 56, 58) comprises in association to all sides of the quadrangular circumferential contour, one respective horizontal ledger (52, 54, 56, 58) detachably connected to two of the vertical posts (32, 34, 36, 38) provided in the four module corner areas (24, 26, 28, 30), in that in the upper post end areas of the vertical posts (32, 34, 36, 38) vertical post connecting members in the form of perforated discs are provided for a detachable connection to the horizontal ledgers (60, 62, 64, 66) of the upper group (Go) of horizontal ledgers (60, 62, 64, 66) and at the lower post end areas of the vertical posts (32, 34, 36, 38) vertical post connecting members in the form of perforated discs are provided for a detachable connection to the horizontal ledgers (52, 54, 56, 58) of the lower group (Gu) of horizontal ledgers (52, 54, 56, 58), wherein the vertical post connecting members provided at the upper post end areas of the vertical posts (32, 34, 36, 38) have a first distance (A 1) to a respective upper vertical post end and the vertical post connecting members provided at the lower post end areas of the vertical posts (32, 34, 36, 38) have a second distance (A 2) to a respective lower vertical post end and all horizontal ledgers (60, 62, 64, 66) of the upper group (Go) of horizontal ledgers (60, 62, 64, 66) are detachably connected to the vertical posts (32, 34, 36, 38) at the same height position and all horizontal ledgers (52, 54, 56, 58) of the lower group (Gu) of horizontal ledgers (52, 54, 56, 58) are detachably connected to the vertical posts (32, 34, 36, 38) at the same height position, in that, in association to at least two immediately adjacent vertical posts (32, 34, 36, 38) a diagonal ledger (72, 74, 76, 78) is provided connected to the vertical post connecting members provided for the connection to the horizontal ledgers (60, 62, 64, 66) of the upper group (Go) of horizontal ledgers (60, 62, 64, 66) and the horizontal ledgers (52, 54, 56, 58) of the lower group (Gu) of horizontal ledgers (52, 54, 56, 58) and is thereby detachably connected thereto. - in each module corner area (24, 26, 28, 30) of the stair scaffolding module (M 1, M 2, M 3) formed with a quadrangular circumferential contour, a vertical post (32, 34, 36, 38) with an upper post end area and a lower post end area, - in the upper post end areas of the vertical posts (32, 34, 36, 38), an upper group (Go) of horizontal ledgers (60, 62, 64, 66) connected thereto, - in the lower post end areas of the vertical posts (32, 34, 36, 38) a lower group (Gu) of horizontal ledgers (52, 54, 56, 58) connected thereto, - a stair unit having an upper stair unit end area and a lower stair unit end area, wherein the upper stair unit end area is detachably connected to a horizontal ledger of the upper group (Go) of horizontal ledgers (60, 62, 64, 66) and the lower stair unit end area is detachably connected to a horizontal ledger of the lower group (Gu) of horizontal ledgers (52, 54, 56, 58), wherein the upper group (Go) of horizontal ledgers (60, 62, 64, 66) on one side of the quadrangular circumferential contour comprises a horizontal ledger for a detachable connection with the upper stair unit end area, and the lower group (Gu) of horizontal ledgers (52, 54, 56, 58) on another side of the quadrangular circumferential contour opposite said one side of the quadrangular circumferential contour comprises a horizontal ledger for a detachable connection with the lower stair unit end area,