A microscope system comprising: a microscope body ; a camera connected to an observation optical system of the microscope body ; and an XY stage on which a slide of an observation object is placed and which is configured to move in an X-axis direction and a Y-axis direction that are orthogonal to each other, wherein the XY stage comprises an XY two-dimensional scale plate , and the XY two-dimensional scale plate comprises: a first mark configured to provide X-axis direction axis information and Y-axis direction axis information of the XY stage; and a second mark which is provided within an observable region of the camera on the same plane as the first mark and which is available for recognizing a position of an XY plane of the first mark in a Z-axis direction at each of a plurality of points by focus detection of the camera characterized in that the second mark is formed from a plurality of focus units each formed from a plurality of pairs of lines with the same width which are arranged to be symmetric with respect to a center line serving as the axis of symmetry while changing the width wherein the second mark forms a rectangle formed from two parallel sides each having a predetermined width along the X-axis direction and two parallel sides each having a predetermined width along the Y-axis direction the second mark and has a predetermined rectangular size capable of representing a slant of a slide placement surface on the XY stage . a microscope body ; a camera connected to an observation optical system of the microscope body ; and an XY stage on which a slide of an observation object is placed and which is configured to move in an X-axis direction and a Y-axis direction that are orthogonal to each other, wherein the XY stage comprises an XY two-dimensional scale plate , and the XY two-dimensional scale plate comprises: a first mark configured to provide X-axis direction axis information and Y-axis direction axis information of the XY stage; and a second mark which is provided within an observable region of the camera on the same plane as the first mark and which is available for recognizing a position of an XY plane of the first mark in a Z-axis direction at each of a plurality of points by focus detection of the camera characterized in that the second mark is formed from a plurality of focus units each formed from a plurality of pairs of lines with the same width which are arranged to be symmetric with respect to a center line serving as the axis of symmetry while changing the width wherein the second mark forms a rectangle formed from two parallel sides each having a predetermined width along the X-axis direction and two parallel sides each having a predetermined width along the Y-axis direction the second mark and has a predetermined rectangular size capable of representing a slant of a slide placement surface on the XY stage . a first mark configured to provide X-axis direction axis information and Y-axis direction axis information of the XY stage; and a second mark which is provided within an observable region of the camera on the same plane as the first mark and which is available for recognizing a position of an XY plane of the first mark in a Z-axis direction at each of a plurality of points by focus detection of the camera characterized in that the second mark is formed from a plurality of focus units each formed from a plurality of pairs of lines with the same width which are arranged to be symmetric with respect to a center line serving as the axis of symmetry while changing the width wherein the second mark forms a rectangle formed from two parallel sides each having a predetermined width along the X-axis direction and two parallel sides each having a predetermined width along the Y-axis direction the second mark and has a predetermined rectangular size capable of representing a slant of a slide placement surface on the XY stage . <EOS>