To provide a three phase voltage regulator which can maintain a positive and negative balance during conduction of each phase and suppress the magnetic noise and unwanted sounds by suppressing the DC excitation when an effective voltage from a three phase power supply is adjusted and controlled.

A pattern selecting means 9 selects a required pattern from a pattern storing means 8 for storing the patterns of switching timing of switching means 3-5 provided on three phase power lines. A timing generating means 10 inputs outputs from a zero-crossing detecting means 6 and a timer 7 in response to the required pattern When the switching means closes, the first closing signal for closing the switching means provided on two phases corresponding to arbitrary phases at a point of time when a voltage between the phases is zero, is outputted. When the electrical angle leads 90 degrees from the point of time of outputting the first closing signal, the second closing signal for closing the switching means on a remaining phase, is outputted. When the switching means opens, the first and second closing signals stop outputting at the point of time that arbitrary phase voltages are almost zero.