The present invention relates to an apparatus and method for performing adjustment to optimize the voltage for each distribution network in a power distribution system. The apparatus for adjusting a voltage in the power distribution system adjusts the voltage by switching a switch that lies on a path in the power distribution system. The apparatus determines a switch that is to become a switching target from among switches lying on the path, obtains a voltage optimization value of the determined switching target switch, selects a switch having the minimum voltage optimization value by changing the switching target switch to another switch in order to obtain the voltage optimization value, and adjusts the voltage through switching of the selected switch.