A pneumatic disc brake device for a railway rolling stock which can produce two times the conventional braking force when the brake cylinder diameter is the same comprises first and second brake levers (1, 2), a pair of brake pads (4) which are mounted through brake heads (5) at one end of the brake levers so as to oppose to a brake disc, and a brake cylinder (6) disposed between the other ends of the first and second brake levers, wherein the brake cylinder (6) comprises a first cylinder part (6a) and a second cylinder part (6b) disposed in series.