A purpose of the present invention is to prevent a PM-caused short circuit between a heating element and a case in an electrically heated catalyst. The electrically heated catalyst is provided in an exhaust gas passage of an internal combustion engine the air-fuel ratio of which is controlled at a ratio near a theoretical air-fuel ratio at an operation time. The electrically heated catalyst includes a heating element that generates heat through electric conduction, a case that stores the heating element therein, and an insulating member sandwiched between the heating element and the case. According to the present invention, the heating element is electrically conducted after the operation of the internal combustion engine is stopped.