PURPOSE: To efficiently continuously manufacture a filter having excellent filtration ability by passing nonwoven fiber web consisting of conductive polymer materials through a high voltage electrical field between an earth electrode and an electrically discharging electrode, bringing the web into contact with the earth electrode, stretching the web and bringing static charge to the web.

CONSTITUTION: A nonwoven fiber web made of conductive polymer materials 30 is prepared and an earth electrode 34 and at least one electrically discharged electrode 32 adjacent to the earth electrode 34 are prepared. A high voltage electrical field is formed between the electrode 32 and the electrode 34 and the web 30 is passed through the high voltage electrical field being stretched. Thereby maintaining the temperature of the web 30 to about a room temperature, the web 30 is brought into contact with the earth electrode 34 so that continuous static charge is brought onto the web 30. Thus the objective filter having excellent filtration ability can continuously and efficiently be manufacture.