A frequency divider for a wireless communication system is provided. A frequency divider includes a body bias voltage generator and a divider. The body bias voltage generator generates a body bias voltage including a PMOS body bias voltage and an NMOS body bias voltage whose voltage levels are controlled according to an input signal. The divider includes a plurality of flip-flops whose operation points are determined according to the body bias voltage, and generates an output signal by dividing a frequency of the input signal by N. Each of the flip-flops may include a PMOS logic and an NMOS logic. The PMOS logic may include a plurality of PMOS transistors whose operation points are determined according to the PMOS body bias voltage. The NMOS logic may be connected electrically to the PMOS logic and include a plurality of NMOS transistors whose operation points are determined according to the NMOS body bias voltage.