According to various embodiments disclosed herein, an electronic device comprises: a front plate including a front surface facing a first direction and a first portion of a side surface extending from the front surface; a frame forming a second portion of the side surface and on which electronic components of the electronic device sit; a rear cover including a rear surface facing a second direction opposite the first direction and a third portion of the side surface extending from the rear surface to the second portion of the side surface; a mmWave antenna module including a mmWave antenna disposed in one region of the frame and configured to form a beam in a third direction forming an obtuse angle with the first direction and an acute angle with the second direction; and a wireless communication circuit electrically connected to the mmWave antenna module. The rear cover comprises a ceramic material. In the third portion of the rear cover, a portion included in a region forming a first angle with the third direction in which the mmWave antenna module is configured to form a beam has a thickness in a first range. A portion outside the region forming a first angle with the third direction in which the mmWave antenna module is configured to form a beam may have a thickness in a second range greater than the first range.