The invention relates to an objective replacement device for a microscope, wherein the sample is located in a sample chamber and surrounded by an immersion medium within the sample chamber, means for positioning and aligning the sample relative to the focus of an objective being present, wherein the detection beam path is aligned horizontally, which is to say perpendicular to the direction of action of gravity. For an objective replacement device for a microscope of the type described above, according to the invention a device is provided for exchanging the objective, at the focus of which the sample is positioned and aligned, with at least another objective, the position and alignment of the sample within the sample chamber remaining the same.