An antenna for a radio base station has a leaky coaxial cable transmitting transmission power toward a terminator and transmitting received power toward an input terminal, a low-loss coaxial cable having a transmission loss per unit length smaller than that of the leaky coaxial cable, a first directional coupler having a function to pass the transmission power advancing to the terminator and a function to output the received power advancing toward the input terminal to the outside, a second directional coupler having a function to pass the transmission power advancing to the terminator and a function to bypass and output the received power advancing to the input terminal to the low-loss coaxial cable, and a power compositor inputting the received power output from the first directional coupler and the received power from the low-loss coaxial cable and outputting its composite power.