Provided is a sintered object which has excellent resistance to corrosion by corrosive halogen gases and by the plasmas thereof and has excellent thermal conductivity and excellent electrical conductivity. The sintered object has few limitations on design, is usable in a wide range of applications, and is highly versatile. The sintered object has no frequency dependence when a high-frequency voltage is applied thereto and with which it is possible to actualize the stability of a plasma. Also provided is a method for producing the sintered object. Furthermore provided is a high-frequency transmission material which has direct-current electrical conductivity for reducing fluctuations in plasma potential and has capacitive properties that enable the material to transmit high-frequency power necessary for plasma excitation, and which has no fear of causing contamination of a sample with a metal and has resistance to corrosion by plasmas.