A sensor includes: a detection element; a separator including an insertion portion into which a rear side of the detection element is inserted, and a plurality of terminal housing portions that are disposed surrounding a circumference of the insertion portion around an axial direction, and extend in the axial direction; and a connection terminal that is electrically connected to an electrical connection terminal portion to form a current path. The connection terminal includes a frame body portion and an element contact portion. The sensor further includes a first regulation portion that is located at a position closer to the detection element relative to the frame body portion, in a direction in which a first main surface and a second main surface oppose each other, and regulates the movement of the frame body portion in a direction approaching the detection element.