Electronic device including pen input device

According to one embodiment of the present invention, an electronic device comprises: a housing including a conductive portion and a first non-conductive portion connected to the conductive portion; an antenna structure located inside the housing and including a printed circuit board including a first surface and a second surface facing in an opposite direction to the first surface, and at least one antenna element located inside the printed circuit board closer to the first surface than the second surface, or located on the first surface; and a pen input device attachable/detachable from the housing, in which, in a state in which the pen input device is attached to the housing taking into account a direction in which a main beam of the antenna structure is radiated, the pen input device includes a second non-conductive portion, at least a portion of which overlaps the first non-conductive portion, and a second non-conductive portion, at least a portion of which overlaps the second non-conductive portion. And