PURPOSE: To attain retrigger by providing a prescribed time constant circuit also to a DFF-B being an auxiliary monostable multivibrator circuit and making a Q output of the DFF-B keep an H level for a prescribed time.

CONSTITUTION: Even when the Q output of a 1st flip-flop (DFF-A) keeps an H level, the Q output of a 2nd flip-flop (DFF-B) changes to an H level by the input of the succeeding clock signal to make the open collector circuit OC-1 of the 1st time constant circuit conductive. Thus, the capacitor C1 of the time constant circuit is discharged once and then starts re-charging, and the leading start point of time of a node XA is reset after the discharge is finished. That is, the H level is kept in the output of the monostable multivibrator circuit for a prescribed time based on the succeeding clock signal, then it means that the retriggering is implemented. Thus, the monostable multivibrator circuit provided with the retrigger function is obtained.