Interest in millimeter-wave(mm-wave) communication technology is increasing. The mm-wave band signal has a short wavelength but a wide bandwidth, which is useful for communication. However, it has strong linearity and high free-space path loss. To overcome this, beamforming technology is required. Beamforming is a technology of electrical tilting a beam without a mechanical motor. If beamforming is applied to the mm-wave system, it can be applied to various fields such as mobile communication as well as vehicle radar. In this paper, a beamforming transmitter at 28GHz is designed. After synchronization between multiple channels, beamforming experiments were conducted. The phase control resolution at 28 GHz is 2.81°, and beamforming is controlled at 1° intervals.