The invention relates to a mixing device with a first chamber (1) for a first component, in particular a powder [a liquid], a second chamber (12) for a second component, in particular a liquid [powder], and a divider means (11, 13) separating the first and the second chamber. The second chamber is defined by an inner hollow cylinder (10) which is arranged so as to be moved in a piston-like fashion in an outer hollow body (2) defining the first chamber. According to the invention, the first chamber comprises an evacuation opening (5) which is adapted to be connected with a vacuum source. The invention further relates to a method for vacuum packaging the mixing device.