An ion exchange membrane for alkali chloride electrolysis comprising a fluoropolymer having ion exchange groups, a reinforcing material embedded in the fluoropolymer and formed of reinforcing yarns and optionally contained sacrificial yarns, and elution holes of the sacrificial yarns present between the reinforcing yarns, characterized in that in a cross section perpendicular to the length direction of the reinforcing yarns forming the reinforcing material, the average distance (d1) from the center of a reinforcing yarn to the center of the adjacent reinforcing yarn is from 750 to 1,000 μm, and the total area (S) obtained by adding the cross-sectional area of an elution hole and the cross-sectional area of a sacrificial yarn remaining in the elution hole is from 500 to 5000 μm 2 per elution hole, and the number n of elution holes between adjacent reinforcing yarns is from 4 to 6, wherein an elution hole formed from one sacrificial yarn made of a multifilament is counted as 1, wherein the average distance (d1) is measured as follows: by observing a cross section cut perpendicular to the length direction of reinforcing yarns, of an ion exchange membrane dried at 90°C for at least 2 hours, by an optical microscope, the distance is measured by using an image software; in the measurement, in each of the MD cross section and the TD cross section, the distance from the center of a reinforcing yarn to the center of the adjacent reinforcing yarn is measured at 10 points; with respect to the MD cross section, the average distance (d1) being an average value of the measured values at 10 points, is obtained; and also with respect to the TD cross section, the average distance (d1) is obtained in the same manner, and wherein the total area (S) is measured as follows: by observing a cross section cut perpendicular to the length direction of reinforcing yarns, of an ion exchange membrane dried at 90°C for at least 2 hours, by an optical microscope, the total area (S) obtained by adding the cross-sectional area of an elution hole and the cross-sectional area of a sacrificial yarn, is measured by using an image software; the total area (S) is measured at 10 points randomly selected in each of the MD cross section and the TD cross section; with respect to the MD cross section, the total area (S) is obtained as an average value of the measured values at 10 points; and also with respect to the TD cross section, the total area (S) is obtained in the same manner. by observing a cross section cut perpendicular to the length direction of reinforcing yarns, of an ion exchange membrane dried at 90°C for at least 2 hours, by an optical microscope, the distance is measured by using an image software; in the measurement, in each of the MD cross section and the TD cross section, the distance from the center of a reinforcing yarn to the center of the adjacent reinforcing yarn is measured at 10 points; with respect to the MD cross section, the average distance (d1) being an average value of the measured values at 10 points, is obtained; and also with respect to the TD cross section, the average distance (d1) is obtained in the same manner, and wherein the total area (S) is measured as follows: by observing a cross section cut perpendicular to the length direction of reinforcing yarns, of an ion exchange membrane dried at 90°C for at least 2 hours, by an optical microscope, the total area (S) obtained by adding the cross-sectional area of an elution hole and the cross-sectional area of a sacrificial yarn, is measured by using an image software; the total area (S) is measured at 10 points randomly selected in each of the MD cross section and the TD cross section; with respect to the MD cross section, the total area (S) is obtained as an average value of the measured values at 10 points; and also with respect to the TD cross section, the total area (S) is obtained in the same manner. <EOS>