PURPOSE: To attain the set of the pulse width of an undesired pulse with high accuracy and to reduce the circuit scale by using a counter so as to set the pulse width in place of a monostable multivibrator in the elimination of the undesired pulse.

CONSTITUTION: The pulse shaping circuit consists of an up-edge detection circuit 10 using the leading of a digital pulse signal 100 as a trigger and outputting a pulse for a prescribed time (t), an down-edge detection circuit 12 using the trailing of the digital pulse signal 100 as a trigger and outputting a pulse for a prescribed time (t), synchronous counters 14, 16 using a clock signal 102 as a clock and using an output signal of the edge detection circuit of the pre-stage as a load signal, AND circuits 18, 20 using an output signal of the edge detection circuits 10, 12 and a data output signal of the most significant digit of the counters 14, 16 as the input signal, an exclusive OR circuit 22 and a flip-flop 24. In this case, the period of the clock signal is shorter than the time (t) and the output signal of the AND circuits 18, 20 is inputted as the clear signal of the counters 16, 14.