An electronic device comprising: a first cover; a second cover coupled with the first cover and configured to perform a sliding operation; a rollable display including a first display region visible in a rolled state and a second display region unrolled in response to the sliding operation of the second cover; a first antenna including a plurality of first antenna elements and disposed in the first display region of the rollable display; a second antenna including a plurality of second antenna elements and disposed in the second display region of the rollable display; and a processor, wherein the processor is configured to: form a plurality of directional beams using the first antenna based on a first beam table in the rolled state of the rollable display, and form a plurality of directional beams using the first antenna and at least a portion of the second antenna elements of the second antenna based on a second beam table based on a size of a visible region of the rollable display increasing from the rolled state, wherein a number of second antenna elements disposed on a front side of the electronic device (101, 102, 104), among the antenna elements (332, 334, 336, 617-1) of the second antenna, changes according to a change in a size of the second display region visible on the front side of the electronic device (101, 102, 104), wherein the processor is further configured to form a plurality of directional beams using the second antenna based on a third beam table in the rolled state of the rollable display, the second antenna being disposed toward a rear side of the electronic device in the rolled state of the rollable display, and in the rolled state of the rollable display, the plurality of directional beams formed using the second antenna are configured to be formed in an opposite direction to the plurality of directional beams formed using the first antenna. a first cover; a second cover coupled with the first cover and configured to perform a sliding operation; a rollable display including a first display region visible in a rolled state and a second display region unrolled in response to the sliding operation of the second cover; a first antenna including a plurality of first antenna elements and disposed in the first display region of the rollable display; a second antenna including a plurality of second antenna elements and disposed in the second display region of the rollable display; and a processor, wherein the processor is configured to: form a plurality of directional beams using the first antenna based on a first beam table in the rolled state of the rollable display, and form a plurality of directional beams using the first antenna and at least a portion of the second antenna elements of the second antenna based on a second beam table based on a size of a visible region of the rollable display increasing from the rolled state, wherein a number of second antenna elements disposed on a front side of the electronic device (101, 102, 104), among the antenna elements (332, 334, 336, 617-1) of the second antenna, changes according to a change in a size of the second display region visible on the front side of the electronic device (101, 102, 104), wherein the processor is further configured to form a plurality of directional beams using the second antenna based on a third beam table in the rolled state of the rollable display, the second antenna being disposed toward a rear side of the electronic device in the rolled state of the rollable display, and in the rolled state of the rollable display, the plurality of directional beams formed using the second antenna are configured to be formed in an opposite direction to the plurality of directional beams formed using the first antenna. form a plurality of directional beams using the first antenna based on a first beam table in the rolled state of the rollable display, and form a plurality of directional beams using the first antenna and at least a portion of the second antenna elements of the second antenna based on a second beam table based on a size of a visible region of the rollable display increasing from the rolled state, wherein a number of second antenna elements disposed on a front side of the electronic device (101, 102, 104), among the antenna elements (332, 334, 336, 617-1) of the second antenna, changes according to a change in a size of the second display region visible on the front side of the electronic device (101, 102, 104), wherein the processor is further configured to form a plurality of directional beams using the second antenna based on a third beam table in the rolled state of the rollable display, the second antenna being disposed toward a rear side of the electronic device in the rolled state of the rollable display, and in the rolled state of the rollable display, the plurality of directional beams formed using the second antenna are configured to be formed in an opposite direction to the plurality of directional beams formed using the first antenna.