Disclosed are a variable antenna and an apparatus for detecting a radio signal. The variable antenna includes: a first receiving unit including at least one liquid metal antenna element; a second receiving unit including at least one liquid metal antenna element having a length different from a length of the first receiving unit; and a gain control unit configured to electrically adjust lengths of the liquid metal antenna elements for one of the first receiving unit and the second receiving unit according to the frequency of a received signal, wherein each antenna array realized by the liquid metal antenna elements of the first receiving unit and the second receiving unit is arranged in a single bay.