The present invention aims to perform optical axis adjustment while a vehicle is stopped only in necessary situations and to avoid unnecessary adjustment, and to further enhance durability. A headlight optical axis adjustment device for adjusting an optical axis of a headlight based on a pitch angle of the vehicle includes an opened/closed state detection section for detecting an open/closed state of an open/close unit where the opened state is when a passenger gets on/out or when a baggage is being loaded/unloaded to and from the vehicle; and an optical axis adjustment permitting section for permitting optical axis adjustment of the headlight based on the pitch angle of the vehicle when the opened state of the open/close unit is detected by the opened/closed state detection section.