Disclosed relates to an electromagnetic interference (EMI) filter. Capacitance and resistance or inductance of an EMI filter, which includes a resistor and a capacitor or an inductor and a capacitor, can be controlled, such that a cutoff frequency can be freely controlled without manufacturing a separate EMI filter according to a characteristic of a desired cutoff frequency. Further, an intelligent EMI filter that can be applied to a surge protection device, which includes an ESD protection function as well as the EMI filter, is provided, such that a process can be simplified and costs can be reduced.