Provided is an antenna for a base station and a repeater capable of electrically or mechanically controlling the individual operation of an element antenna constituting an array antenna or a sub-array antenna so as to adaptively cope with the change in the communication environment, and having an economic and high performance transmitting and receiving function, and a method of controlling a mode of the antenna. The multi-mode antenna includes a radiation portion having one or more array antenna and capable of selectively changing an antenna effective opening surface and changing a resistance direction of an antenna beam pattern, an active channel portion connected to the array antennas and including switches, transmission and receiving channels, and a signal combiner and splitter, and a modem and control portion connected to the active channel portion and having a control portion and a modem.