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 (213, 292, 293) configured to provide X-axis direction axis information and Y-axis direction axis information of the XY stage; and a second mark (294, 295, 296) which is provided within an observable region of the camera on the same plane as the first mark (213, 292, 293) and which is available for recognizing a position of an XY plane of the first mark (213, 292, 293) in a Z-axis direction at each of a plurality of points by focus detection of the camera characterized in that the second mark (294, 295, 296) is formed from a plurality of focus units (297, 298) 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 (294, 295, 296) 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 (294, 295, 296) 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 (213, 292, 293) configured to provide X-axis direction axis information and Y-axis direction axis information of the XY stage; and a second mark (294, 295, 296) which is provided within an observable region of the camera on the same plane as the first mark (213, 292, 293) and which is available for recognizing a position of an XY plane of the first mark (213, 292, 293) in a Z-axis direction at each of a plurality of points by focus detection of the camera characterized in that the second mark (294, 295, 296) is formed from a plurality of focus units (297, 298) 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 (294, 295, 296) 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 (294, 295, 296) and has a predetermined rectangular size capable of representing a slant of a slide placement surface on the XY stage. a first mark (213, 292, 293) configured to provide X-axis direction axis information and Y-axis direction axis information of the XY stage; and a second mark (294, 295, 296) which is provided within an observable region of the camera on the same plane as the first mark (213, 292, 293) and which is available for recognizing a position of an XY plane of the first mark (213, 292, 293) in a Z-axis direction at each of a plurality of points by focus detection of the camera characterized in that the second mark (294, 295, 296) is formed from a plurality of focus units (297, 298) 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 (294, 295, 296) 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 (294, 295, 296) and has a predetermined rectangular size capable of representing a slant of a slide placement surface on the XY stage.