A measuring method for obtaining a reference point on a table center of an inclined rotating table in a wire electric discharge machine using a measuring jig (10, 20), the wire electric discharge machine taking, as an X-axis, a direction of lateral movement on a horizontal plane of the wire electric discharge machine that machines a workpiece by moving a wire electrode and the workpiece relative to each other while supporting the wire electrode with upper and lower wire guides (75, 63), taking, as a Y-axis, a direction of longitudinal movement on the horizontal plane which is perpendicular to the X-axis, and taking, as a Z-axis, a direction of vertically upward movement, a biaxial rotation unit being placed on a table of the wire electric discharge machine, the biaxial rotation unit including a first rotating table which rotates a work fixing section that fixes a workpiece and a second rotating table which rotates about an axis orthogonal to the rotating table and inclines a workpiece with respect to an X-Y plane, the measuring jig (10, 20) including a fixed section (11,21) for being fixed to the work fixing section, an arm section (12, 22) which is provided to stand on the fixed section, and a section to be measured (13, 23) which is provided at a distal end of the arm section and has a conductive spherical surface, the measuring method comprising: a step of measuring a height (15, h1) from a bottom surface of the fixed section (11, 21) of the measuring jig (10, 20) to a distal end of the spherical surface in the section to be measured of the measuring jig; a step of acquiring an angle of inclination of the second rotating table; a step of fixing the measuring jig (10, 20) to the work fixing section; a step of measuring a height from a table surface of the wire electric discharge machine to an upper end of the spherical surface; a step of bringing the wire electrode into contact with the spherical surface from opposing directions on a same straight line and measuring two points on the spherical surface; a step of bringing the wire electrode into contact with the spherical surface from a direction along a straight line which passes through a midpoint of the obtained two points and intersects the straight line at right angles and measuring one point on the spherical surface; a step of obtaining a center point position on the X-Y plane of the spherical surface on the basis of positions of the measured three points; and a step of calculating coordinates of a reference point on a table center of the second rotating table from the height (15, h1) from the bottom surface of the fixed section (11, 21) to the distal end of the spherical surface, the height from the table surface of the discharge machine to the upper end of the spherical surface, the angle of inclination of the second rotating table, and the center point position on the X-Y plane of the spherical surface, which are measured. a step of measuring a height (15, h1) from a bottom surface of the fixed section (11, 21) of the measuring jig (10, 20) to a distal end of the spherical surface in the section to be measured of the measuring jig; a step of acquiring an angle of inclination of the second rotating table; a step of fixing the measuring jig (10, 20) to the work fixing section; a step of measuring a height from a table surface of the wire electric discharge machine to an upper end of the spherical surface; a step of bringing the wire electrode into contact with the spherical surface from opposing directions on a same straight line and measuring two points on the spherical surface; a step of bringing the wire electrode into contact with the spherical surface from a direction along a straight line which passes through a midpoint of the obtained two points and intersects the straight line at right angles and measuring one point on the spherical surface; a step of obtaining a center point position on the X-Y plane of the spherical surface on the basis of positions of the measured three points; and a step of calculating coordinates of a reference point on a table center of the second rotating table from the height (15, h1) from the bottom surface of the fixed section (11, 21) to the distal end of the spherical surface, the height from the table surface of the discharge machine to the upper end of the spherical surface, the angle of inclination of the second rotating table, and the center point position on the X-Y plane of the spherical surface, which are measured.