A clock driver is provided. A first driving unit is configured with a plurality of drivers and receives a first clock signal to drive a first pumping clock. A second driving unit is configured with a plurality of drivers and receives a second clock signal to drive a second pumping clock. A charge recycling switch is connected between an output terminal of the first driving unit and an output terminal of the second driving unit. A switch controller selectively transfers an input clock signal of the first or second driving unit to the charge recycling switch in response to the first and second pumping clock signals.