Abstract: The invention relates to a device for blood separation by squeezing out blood components from a blood bag (29) having at least one outlet conduit (30), said device comprising a support surface (1) and a pressure surface (3) being movable relatively to the support surface and arranged for compressing a blood bag (29) inserted between the pressure surface (3) and the support surface (1). The pressure surface (3) is arranged essentially in parallel with the support surface (1) and drive means are provided for displacement of the pressure surface (3) substantially perpendicularly to the support surface (1) for compressing the blood bag (29) essentially uniformly over the entire surface thereof, and it is provided with at least one sensing device (17, 18), which is arranged to detect when a pre-selected blood component layer has reached a given level in the blood bag (29) and in response thereto to activate means (20) for shutting-off at least one of said outlet conduits (30).