Electricity is suppressed from flowing to a case (4) of an electrically heated catalyst (1). Provision is made for a heat generation element (2) to be electrically energized to generate heat, the case (4) in which the heat generation element (2) is contained, a mat (5) arranged between the heat generation element (2) and the case (4), an electrode (6) connected to the heat generation element (2) from outside of the case (4), an insulation part (7) to plug a gap between the case (4) and the electrode (6), an electrode chamber (8) which is a space formed around the electrode (6) at an inner side of the case (4) and at an outer side of the heat generation element (2), and which is formed by providing a gap between the electrode (6) and the mat (5), and a circulation passage (9) which is provided with two opening portions (91) either at an upstream side or at a downstream side of the heat generation element (2), and which is connected from one of the opening portions (91) to the other of the opening portions (91) while passing through around said electrode (6).