Recently, radio-wave sensors have been utilized in automotive radar and biological sensing applications. Although beamforming using an array antenna is effective method for changing the radiation directivity, the phase-shift error causes degradation of the directivity significantly. In this paper, we propose a fine-tuning phase shifter with a vector synthesizer, which enables to control the phase-shift amount continuously in 24-GHz band. From the measurement results of the fabricated phase shifter using 65-nm CMOS technology, the variable phase-shift amount over a range of 360 degrees is obtained continuously. In addition, the estimated radiation patterns show that the phase-shift and amplitude errors of the fabricated phase shifter are acceptable.