Provided is a quadrature voltage controlled oscillator having only one resonant mode characteristic. The quadrature voltage controlled oscillator has a structure in which two clocks generated from respective LC resonant circuits are 90 degrees out of phase with each other using a phase detector and a loop filter, instead of a general structure in which two LC tank resonant circuits are mutually coupled to constitute an LC quadrature voltage controlled oscillator. The quadrature voltage controlled oscillator includes two resonant circuits having the same oscillation frequency; and a phase controller receiving oscillation clocks of the two resonant circuits to control at least one of oscillation phases of the two resonant circuits according to a phase difference between the two oscillation clocks.