In this study, we present a 4T (transmit) 4R (receive) base station antenna for 5G. Furthermore we design, manufacture, and analyze phase-adjustable antennas that allow four RF signals supplied from the base station equipment to match the phase of each of the four ports of the antenna. The bandwidth was designed based on the 5G band (3,400∼3,700 MHz) used by three mobile telecommunication companies. The radiation element of the antenna is configured to supply power to four ports consisting of two columns of dual polarization 10 arrays. Each transmission line fed to the four ports has a phase controller that can control the phase of the port, and each transmission line that has passed through it includes a module that includes a coupler that separates small signals and a coupler to combine into one. The combined signal was connected to a connector for signal detection outside the antenna and used as a test port. Using this configuration, the phase of the signal supplied from the base station equipment to each port of the antenna can be adjusted equally, and the phase difference for each port can be realized within 5°. Thus, separate services for each port and combined services of the ports were freely implemented without significant loss to enable beamforming.