A window blind (1, 2), comprising: a fixed rail (10, 51); a plurality of slats (12, 54), which are horizontally hanged below the fixed rail through at least one ladder tape (11, 53), each of which has a front tape body (11a, 53a) and a rear tape body (11b, 53b); an input mechanism adapted to control at least one lifting cord (13, 55), so as to raise or lower the slats (12, 54) to collect or expand the window blind (1, 2); an output adjustment mechanism provided in the fixed rail (10, 51), wherein the output adjustment mechanism is adapted to operate with the input mechanism simultaneously; a first shaft provided in the fixed rail (10, 51), wherein an end of the first shaft is connected to the output adjustment mechanism; the output adjustment mechanism is adapted to be driven by the input mechanism to rotate the first shaft, whereby to relative move the front tape body (11a, 53a) and the rear tape body (11b, 53b) of each of the at least one ladder tape (11, 53) in a vertical direction, changing the slats (12, 54) between a first state and a second state; and a second shaft provided in the fixed rail (10, 51), wherein, when the second shaft is driven by the input mechanism to roll up the at least one lifting cord (13, 55) to move a lowest slat (12, 54) among the slats (12, 54) toward the fixed rail (10, 51), the slats (12, 54) are in the first state; when the the second shaft is driven by the input mechanism to release the at least one lifting cord (13, 55) to move the lowest slat (12, 54) among the slats (12, 54) away from the fixed rail (10, 51), the slats (12, 54) are in the second state, characterized in that the input mechanism comprises a transmission member, which is adapted to be rotated in a direction or in another opposite direction; the output adjustment mechanism comprises an adjustment output wheel and an adjustment driven wheel, wherein the first shaft is connected to the adjustment driven wheel; the adjustment output wheel is adapted to rotate along with the transmission member to rotate the adjustment driven wheel, whereby the adjustment driven wheel is adapted to drive the first shaft to rotate. a fixed rail (10, 51); a plurality of slats (12, 54), which are horizontally hanged below the fixed rail through at least one ladder tape (11, 53), each of which has a front tape body (11a, 53a) and a rear tape body (11b, 53b); an input mechanism adapted to control at least one lifting cord (13, 55), so as to raise or lower the slats (12, 54) to collect or expand the window blind (1, 2); an output adjustment mechanism provided in the fixed rail (10, 51), wherein the output adjustment mechanism is adapted to operate with the input mechanism simultaneously; a first shaft provided in the fixed rail (10, 51), wherein an end of the first shaft is connected to the output adjustment mechanism; the output adjustment mechanism is adapted to be driven by the input mechanism to rotate the first shaft, whereby to relative move the front tape body (11a, 53a) and the rear tape body (11b, 53b) of each of the at least one ladder tape (11, 53) in a vertical direction, changing the slats (12, 54) between a first state and a second state; and a second shaft provided in the fixed rail (10, 51), wherein, when the second shaft is driven by the input mechanism to roll up the at least one lifting cord (13, 55) to move a lowest slat (12, 54) among the slats (12, 54) toward the fixed rail (10, 51), the slats (12, 54) are in the first state; when the the second shaft is driven by the input mechanism to release the at least one lifting cord (13, 55) to move the lowest slat (12, 54) among the slats (12, 54) away from the fixed rail (10, 51), the slats (12, 54) are in the second state, characterized in that the input mechanism comprises a transmission member, which is adapted to be rotated in a direction or in another opposite direction; the output adjustment mechanism comprises an adjustment output wheel and an adjustment driven wheel, wherein the first shaft is connected to the adjustment driven wheel; the adjustment output wheel is adapted to rotate along with the transmission member to rotate the adjustment driven wheel, whereby the adjustment driven wheel is adapted to drive the first shaft to rotate.