Abstract: A common mode filter is provided. A common mode filter according to an exemplary embodiment of the present invention comprises: a ring-shaped magnetic core made of a magnetic material and installed so as to be positioned in an arrangement hole which is formed through a circuit board in a predetermined area; a plurality of coils wound around an outer surface of the magnetic core; and a base member to which the magnetic core having the plurality of coils wound thereon is coupled, and having a plurality of connector members for electrically connecting the plurality of coils to the outside, wherein the base member is installed such that a portion thereof is caught on an edge side of the arrangement hole.