This paper presents a 60GHz power amplifier using a capacitive cross-coupling neutralization. The capacitive cross-coupling neutralization contributes to improve power gain and reverse isolation. Moreover, the transmission line for matching networks is optimized to achieve highly power-efficient amplifier. The 3-stage differential power amplifier is fabricated in a 65nm CMOS process and evaluated with 1.2V power supply. The power amplifier achieves power gain of 23.2 dB, output power of 10dBm at 1 dB compression point, saturated output power of 14.6 dBm, peak PAE of 16.3%, and power consumption of 135 mW.