Certain embodiments of the disclosure relate to a device and a method for increasing the efficiency of an antenna of an electronic device that includes a rollable display. The electronic device may include: a processor; a first housing, in which the processor is disposed, including a first conductive portion; a second housing configured to slide in a first direction from the first housing and including a second conductive portion; a rollable display, at least a portion of which is exposed in a slide-out manner according to movement of the second housing; and a variable element disposed in the second housing and is electrically connected to the second conductive portion. The processor may adjust an electrical characteristic of the variable element in response to sliding of the second housing. The disclosure may further include various other embodiments.