A window blind, comprising: an upper beam; a lower beam, located below the upper beam; two ladder-like ropes, connected between the upper beam and the lower beam, each said ladder-like rope having a front vertical portion, a rear vertical portion, a plurality of transverse portions, a plurality of first ring portions, a plurality of second ring portions, and a plurality of third ring portions, the front vertical portion and the rear vertical portion being parallel to each other, the plural transverse portions being vertically equidistant and connected between the front vertical portion and the rear vertical portion, the plural first ring portions being vertically equidistant and connected to the front vertical portion, the plural second ring portions being vertically equidistant and connected to the rear vertical portion, the plural third ring portions being vertically equidistant and connected to the front vertical portion so that the plural third ring portions and the plural first ring portions are located at two opposite sides of the front vertical portion; two pairs of lifting cords, extending downward from the upper beam and having their bottoms connected to the lower beam, one said lifting cord of each said pair passing through the plural first ring portions of one said ladder-like rope, the other lifting cord of each said pair passing through the plural second ring portions of one said ladder-like rope; and a plurality of slats being parallel to each other, connected between the upper beam and the lower beam and mounted on the transverse portions of the two ladder-like ropes, respectively, each said slat having two ends thereof each provided with a through hole and a slot, the through hole being adjacent to a front edge of the slat and receiving one segment of the third ring portion of one said ladder-like rope, so that the front edges of the slats are linked together by the third ring portions of the ladder-like rope, the slot extending from one side of the slat and being communicated with the through hole and allowing the segment of the third ring portion of one said ladder-like rope to pass therethrough; wherein the slot extends from the front edge of the slat to be communicated with the through hole, the slot has a first extending segment and a second extending segment that is perpendicular to the first extending segment, the first extending segment extending from the front edge of the slat in a width direction of the slat to a rear edge of the slat, and the second extending segment extending from one end of the first extending segment in a length direction of the slat to the through hole and is communicated with the through hole, the through hole has a round cross-section. characterized in that the through hole is located between the front edge of the slat and the second extending segment of the slot, so that the through hole is tangent to the second extending segment of the slot. an upper beam; a lower beam, located below the upper beam; two ladder-like ropes, connected between the upper beam and the lower beam, each said ladder-like rope having a front vertical portion, a rear vertical portion, a plurality of transverse portions, a plurality of first ring portions, a plurality of second ring portions, and a plurality of third ring portions, the front vertical portion and the rear vertical portion being parallel to each other, the plural transverse portions being vertically equidistant and connected between the front vertical portion and the rear vertical portion, the plural first ring portions being vertically equidistant and connected to the front vertical portion, the plural second ring portions being vertically equidistant and connected to the rear vertical portion, the plural third ring portions being vertically equidistant and connected to the front vertical portion so that the plural third ring portions and the plural first ring portions are located at two opposite sides of the front vertical portion; two pairs of lifting cords, extending downward from the upper beam and having their bottoms connected to the lower beam, one said lifting cord of each said pair passing through the plural first ring portions of one said ladder-like rope, the other lifting cord of each said pair passing through the plural second ring portions of one said ladder-like rope; and a plurality of slats being parallel to each other, connected between the upper beam and the lower beam and mounted on the transverse portions of the two ladder-like ropes, respectively, each said slat having two ends thereof each provided with a through hole and a slot, the through hole being adjacent to a front edge of the slat and receiving one segment of the third ring portion of one said ladder-like rope, so that the front edges of the slats are linked together by the third ring portions of the ladder-like rope, the slot extending from one side of the slat and being communicated with the through hole and allowing the segment of the third ring portion of one said ladder-like rope to pass therethrough; wherein the slot extends from the front edge of the slat to be communicated with the through hole, the slot has a first extending segment and a second extending segment that is perpendicular to the first extending segment, the first extending segment extending from the front edge of the slat in a width direction of the slat to a rear edge of the slat, and the second extending segment extending from one end of the first extending segment in a length direction of the slat to the through hole and is communicated with the through hole, the through hole has a round cross-section.