A window blind includes a fixed rail and a plurality of slats hang below the fixed rail through a ladder tape. The slats are controlled by an output adjustment mechanism to change between a first state and a second state. In addition, an output clutch mechanism is provided to collect or to expand the window blind. Said output adjustment mechanism and said output clutch mechanism are both controlled by an input mechanism. Whereby, it requires only one single control module to adjust shielding of the slat assembly composed of the slats, and to expand or collect the slat assembly.