The present disclosure relates to a communication technique for converging, with IoT technology, a 5G communication system for supporting a higher data transfer rate beyond the 4G system, and a system therefor. The present disclosure may be applied to intelligent services (for example, smart homes, smart buildings, smart cities, smart cars or connected cars, healthcare, digital education, retail businesses, security- and safety-related services, etc.) on the basis of 5G communication technology and IoT-related technology. Disclosed is a cover device for protecting an antenna device which is mounted in an electronic device to radiate a beam in an ultrahigh-frequency band, the cover device comprising: a cover frame including an open window region corresponding to a radiation region of the antenna device; and a thickness compensation structure disposed in the window region on the cover frame and having a different thickness according to the frequency band of the beam radiated from the antenna device.