OPTICAL AXIS ADJUSTMENT DEVICE

An optical axis adjustment device for a headlamp unit to be mounted in a vehicle is configured to adjust an optical axis of the headlamp unit. and the optical axis adjustment device includes a load information acquirer, a displacement amount calculator, and an optical axis adjuster. The load information acquirer is configured to acquire load information indicating a load on an engine of the vehicle. The displacement amount calculator is configured to calculate a displacement amount of the optical axis on a basis of the load information. The optical axis adjuster is configured to adjust the optical axis of the headlamp unit on a basis of the displacement amount.