1. A microscope system used for acquiring an image of a sample comprising: a first image pickup device configured to acquire an image of the sample; a second image pickup device configured to acquire an image of the sample for calculating focus control information, the second image pickup device having a focus measurement area; an optical path length changing member disposed adjacent the focus measurement area of the second image pickup device; a focus controller; an objective lens; and a driving device controllable by the focus controller and configured to drive the objective lens for adjusting a focal point; wherein the focus measurement area of the second image pickup device includes a first image pickup area and a second image pickup area, the focus controller is configured to analyze the images received by the first image pickup area and the second image pickup area of the second image pickup device and to acquire the focus control information, the focus controller is configured to adjust the focal point by driving the objective lens using the driving device on the basis of the focus control information, and the first image pickup device is configured to acquire an image of the sample.