Electricity is suppressed from flowing to a case (4) of an electrically heated catalyst (1). Provision is made for a heat generation element (2) adapted 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) to insulate electricity and at the same time to support the heat generation element (2), 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 partition part (9) arranged in the electrode chamber (8) at an upstream side of the electrode (6) in a direction of flow of an exhaust gas, in such a manner that the exhaust gas flowing through the interior of the electrode chamber (8) impinges against the partition part (9).