A voltage adjustment device, a voltage adjusting method and a power control system for a distribution system are provided, in which the voltage adjustment device and a static var compensator are appropriately operated in a coordinated manner and the sustention of voltage and the enhancement of the operation efficiency are attained. A voltage adjustment device for a distribution system is installed in the distribution system including a static var compensator on an end side and controls a secondary voltage to be within a predetermined limit value by adjusting a tap position. The voltage adjustment device includes a first unit configured to estimate the secondary voltage; a second unit configured to obtain a corrected voltage by correcting the estimated secondary voltage by using a correction amount obtained from an output of the static var compensator; and a third unit configured to compare the corrected voltage with the predetermined limit value and operate the tap position when the corrected voltage deviates from the predetermined limit value.