PURPOSE: To obtain a delay clock with a waveform having no disturbance and with a desired duty ratio by delaying an input clock by a desired time through the operation in a short time.

CONSTITUTION: The low frequency delay circuit giving an optional delay to an inputted clock and outputting the delayed signal consists of a delay generating means comprising a 1st monostable multivibrator 14 outputting a lock whose pulse width depends on a time constant upon the receipt of the clock, a 1st capacitor being one factor of the time constant and a 1st variable resistor means 15 varying the said time constant by varying its resistance, and of a duty ratio correction means comprising a 2nd monostable multivibrator 19 receiving a delay clock whose pulse width depends on a time constant upon the receipt of the clock from the said 1st monostable multivibrator, a 2nd capacitor being one factor of the said time constant and a 2nd variable resistor 20 means varying the said time constant by varying its resistance.