A window blind includes a headrail and a covering structure provided below the headrail. The covering structure includes multiple slats, which can be turned, lifted, and lowered. A driving module is immovably provided in the headrail and includes a power unit. A modulation assembly includes an adjustment member which is drivable to drive an adjustment cord assembly, turning the slats. A block and tackle system is provided in the headrail, and includes a movable member, which is drivable by the power unit to optionally reciprocate in a longitudinal direction of the headrail. A lifting cord assembly is connected to the block and tackle system, and extends out of the headrail to be fixedly connected to a bottom of the covering structure. When the movable member reciprocates in the longitudinal direction, the lifting cord assembly is driven to lift or lower the covering structure.