To provide an automatic voltage regulator capable of preventing an on-load tap-changing transformer 12 from burnout by detecting the mistake of connection to a tap-changer motor operating mechanism.

The automatic voltage regulator is provided with a tap-change commanding unit 20 for outputting boost tap-changing command or reducing tap-changing command to the on-load tap-changing transformer in accordance with the change of a system voltage; a voltage swing propriety deciding unit 21 for confirming whether the change of system voltage coping to the tap-changing command outputted from the tap-change commanding unit 20 is generated or not; an alarm outputting unit 23 for outputting an alarm when a change is not the change of system voltage coping to the tap-changing command outputted from the tap-change commanding unit 20; and a command output regulating unit 24 for outputting while converting the boost tap-changing command or the reducing tap-changing command to the on-load tap-changing transformer, when the change of the system voltage is the reverse of the tap-changing command outputted from the tap-changing commanding unit.