A voltage controlled oscillator (VCO) was designed for millimeter-wave band frequency synthesizer. The oscillation frequency was enhanced and the minimum required loop gain was decreased compared to the conventional structure by using the distributed LC tank. Frequency tuning range was enhanced by optimizing the design of capacitance in the LC tank. Differential inductor was designed and modeled for millimeter-wave band using electromagnetic simulator. The quality factor and phase noise was improved due to the proposed inductor. The design is based on SMIC 40 nm 1P6M RF CMOS process. Post-simulation shows that the VCO has a tuning range of 5.1 GHz (8.7%) from 56.1 GHz to 61.2 GHz. The phase noise is -88 dBc/Hz at 1 MHz offset at the center frequency. The VCO consumes 3.3 mW from a 0.8 V power supply and the chip area is 0.013 5 mm.