There is provided an apparatus for duty cycle correction. The apparatus for duty cycle correction comprises a moving sum unit performing a moving sum calculation with respect to the square-wave signal and outputting the moving sum signal subjected to moving sum calculation, a comparison unit comparing the moving sum signal with a predetermined threshold voltage, outputting a high signal or low signal, a mean value calculation unit calculating the mean value of an output signal outputted from the comparison unit, the output signal being included in a section having a period integer times greater than that of the square-wave signal, and a threshold voltage control unit comparing the mean value with a middle value, increasing the threshold voltage when the mean value is greater than the middle value, and decreasing the threshold voltage when the mean value is less than the middle value.