A retriggable multivibrator is disclosed which comprises a first delay circuit (3) connected for delay­ing an input signal a predetermined time, a second delay circuit (5) connected to receive an output of the first delay circuit and having a set or a rest function, a flip-flop circuit (2) connected to be set or reset in accordance with an input signal and output signal which comes from the second delay circuit (5) and control circuit (6) connected to detect a reentry of an input signal within a predetermined delay time of the first and second delay circuits and to set or reset the second delay circuit.