A Voltage Controlled Oscillator (VCO) includes a plurality of oscillation units connected in cascade to form a chain; and a plurality of current source sections operatively connected to the oscillation units, the current source sections each being configured to control current provided to the oscillation units, wherein each of the current source sections includes: at least one fixed current source configured to perform a current control of a corresponding oscillation unit by using a fixed voltage; and at least one variable current source configured to perform a current control of the corresponding oscillation unit by using a variable voltage.