Abstract: A ceramic substrate includes: a plate-shaped substrate main body made of an insulating ceramic material; and a metallization layer primarily made of a conductive material, and formed over an entire perimeter of a surface of the substrate main body, along an outer edge of the surface. The ceramic substrate further includes: a composite material layer interposed between the substrate main body and the metallization layer, formed along the outer edge, and containing a ceramic material that is the same as the ceramic material of the substrate main body, and a conductive material that is the same as the conductive material of the metallization layer; and electrode pads primarily made of a conductive material, and formed at a position on the surface, inward of the metallization layer and the composite material layer, and spaced apart from the metallization layer and the composite material layer.