An underground space structure of a buried radio device includes an underground space, a metallic cover on the underground space, and an emission surface having a ring area including a structure material with transmission of electrical waves surrounding the cover. An underground radio device includes an underground antenna arranged apart from the cover in the underground and a radio device connected to the antenna. A radio device on the ground includes an antenna on the ground and a radio device connected to the antenna. The underground antenna and the antenna on the ground are connected via the emission surface including the ring area.