An electromagnetic wave detector includes a semiconductor layer, an insulating layer disposed on the semiconductor layer and having an opening, a two-dimensional material layer extending from on the opening to on the insulating layer, including a connection part in contact with a peripheral part of the insulating layer facing the opening, and electrically connected to the semiconductor layer, a first electrode part disposed on the insulating layer and electrically connected to the two-dimensional material layer, a second electrode part electrically connected to the semiconductor layer, and a unipolar barrier layer disposed between the semiconductor layer and the connection part of the two-dimensional material layer and electrically connected to each of the semiconductor layer and the two-dimensional material layer.