A protection device includes a semiconductor substrate including a protection element; an insulating layer covering a surface of the semiconductor substrate; a conductive layer disposed in the insulating layer, and extending in a plane that is parallel with the surface of the semiconductor substrate; a passive element formed with an elongated conductor, curved in a plane that is parallel with the conductive layer, and located over the conductive layer; and an input terminal, an output terminal, and a ground terminal exposed in a surface of the insulating layer. One end of the passive element is electrically connected to the input terminal, the other end of the passive element and a high-potential-side terminal of the protection element are electrically connected to the output terminal, and a low-potential-side terminal of the protection element and the conductive layer are electrically connected to the ground terminal.