A mounting table body made of ceramic includes power-receiving conductor portions and buried therein. A surface of mounting table body is formed with a recessed connection hole and a connection terminal electrically jointed to the power-receiving conductor portion and exposed into the connection hole, the connection terminal being made of a high-melting-point metal, an alloy thereof or a compound thereof. A power-feeding line member provided with a power-feeding connector portion is inserted at its leading end portion into the connection hole to feed electricity to the power-receiving conductor portion. A stress relaxing member is interposed between the connection terminal and the power-feeding connector portion. The stress relaxing member and the connection terminal are jointed together by a brazing material. The stress relaxing member is made of a metal free from cobalt and nickel or an alloy thereof.