A phase synchronization apparatus includes a bias control unit configured to sequentially delay an input clock signal to generate bias control signals having multiple bits, a bias generation unit configured to generate a pull-up bias voltage having a level that corresponds to logical values of the bias control signals, and to generate a pull-down bias voltage in response to a control signal; and a voltage controlled oscillator configured to include a plurality of delay cells respectively having a pull-up terminal and a pull-down terminal to generate an output clock signal in response to the control voltage, wherein the pull-up bias voltage is supplied to the pull-up terminals of the respective delay cells and the pull-down bias voltage is supplied to the pull-down terminals of the respective delay cells.