PURPOSE: To obtain the three-phase on-load voltage phase compensating transformer which is small, lightweight and low-cost by a method wherein a three-phase-type on-load tap changer can be used as both on-load tap changers for voltage adjustment and for phase adjustment.

CONSTITUTION: A main transformer is provided with a primary main winding 3, with a tap winding 4 for voltage adjustment, with a secondary winding 5 and with a delta- connection tertiary winding 6. A phase shifter is provided with a delta-connection exciting winding 10, with a tap winding 15 for phase adjustment and with a delta- connection stabilizing winding 9. The tap winding 4 for voltage adjustment is connected in series with the neutral-point side of the primary main winding 3 so as to become the same phase, and a delta connection is constituted. A three-phase-type on-load tap changer 13 for voltage adjustment is attached to the neutral-point part. In addition, the tap winding 15 for phase adjustment is connected to a terminal used to release the neutral point of the secondary winding 5 so as to obtain a phase difference of 90° from the secondary winding 5, and a delta connection which is provided with a phase-shifting winding is constituted. A three-phase-type on-load tap changer 16 for phase adjustment is attached to the tap winding 15 for phase adjustment.