A wiring substrate includes a substrate main body which is formed of a ceramic laminate and has a rectangular shape in plan view, and which has a front surface and a back surface and has four side surfaces, each being located between the front surface and the back surface, and having a groove surface located on a side toward the front surface and a fracture surface located on a side toward the back surface; and a metalized layer which is formed on the front surface of the substrate main body so as to extend along the four side surfaces, and which has a rectangular frame shape in plan view, wherein a horizontal surface of the ceramic laminate of the substrate main body is exposed between the metalized layer and the groove surface of each side surface of the substrate main body.