Variable format offset printing machine having a central impression cylinder The printing machine comprises a central impression cylinder (1) on which a web printable substrate (B) is supported and a plurality of printing stations arranged around the central impression cylinder (1). Each printing station comprises a blanket cylinder (2) of variable diameter, a plate cylinder (3) of variable diameter, and an offset inking unit (4). Said blanket cylinder (2), plate cylinder (3) and offset inking unit (4) are individually movable between respective withdraw positions and respective multiple working positions for different diameters of the blanket and plate cylinders (2, 3). At least one of said printing stations has the axis of the blanket cylinder (2) and the axis of the plate cylinder (3) comprised in an inclined first plane (P1) which does not comprise the axis of the central impression cylinder (1) at any of said multiple working positions for different diameters of the blanket and plate cylinders (2, 3).