In an electrically heated catalyst, an electrode is connected to a heat generating element while passing through a through-hole which is formed through a case and an electrode chamber which is formed between an inner wall surface of the case and an outer circumferential surface of the heat generating element. Further, a support member, which is formed of an electric insulator material and which supports the electrode in the through-hole formed through the case, extends along the electrode to the inside of the electrode chamber.