A frequency divider may include: a core circuit including a first flip-flop loop and a second flip-flop loop, wherein each of the first flip-flop loop and the second flip-flop loop divides a frequency of a clock signal received via a control terminal of a flip-flop, wherein the core circuit is configured to: output a frequency-divided signal, based on a first signal output by the first flip-flop loop and a second signal output by the second flip-flop loop, the first and second signals having same frequency-division ratios and different phases, and feed back the frequency-divided signal via an input terminal of each of the first and second flip-flop loops; a duty correction circuit that receives the frequency-divided signal and outputs a differential output signal that is generated by correcting a duty ratio of the frequency-divided signal; and an output circuit that outputs a first output signal, which is a signal amplified from the differential output signal, and a second output signal that is a quadrature signal of the first output signal.