a built - in antenna module includes a main board including a feed pad , a ground pad , and a ground layer having a predetermined area ; an antenna radiator installed on the main board to have a predetermined height , and including a feed pin and a ground pin , the feed pin and the ground pin being electrically connected to the feed pad and the ground pad of the main board , respectively ; a conductor disposed on an inner surface of a case frame and having a predetermined area and thickness , the case frame providing an installation space for the main board and forming an exterior of the terminal ; and at least one electrical connection unit interposed between the conductor and the main board and serving as a medium that electrically connects the conductor to the ground pad and the ground layer of the main board .