A device of correcting duty cycle includes: a duty cycle correcting circuit, a controller of the duty cycle correcting circuit and a duty cycle detecting circuit. The duty cycle correcting circuit generates a pair of phase-shifting clocks in accordance with a pair of complementary clocks and regenerates a regenerated clock in accordance with the pair of phase-shifting clocks. The controller of the duty cycle correcting circuit couples to the duty cycle correcting circuit. The duty cycle detecting circuit couples to the duty cycle correcting circuit and the controller of the duty cycle correcting circuit, and generates a detecting output to the controller of the duty cycle correcting circuit in accordance with a current duty cycle of the regenerated clock. The controller of the duty cycle correcting circuit controls the duty cycle correcting circuit in accordance with the detecting output to adjust the pair of phase-shifting clocks.