1. A projector comprising: a projection section adapted to project a projection image on a projection surface, the projection surface including a target part; a detection section adapted to detect a distance from a predetermined position to the target part of the projection surface; and a control section adapted to set a partial area in the projection image based on the distance, and change a display state of the projection image so that the partial area is masked, the partial area being projected on a part of the projection surface other than the target part.