PURPOSE: To easily make a circuit into a high density integrated circuit by providing a D-FF with a clear terminal and inputting an AND signal to the clock terminal and inputting a OR signal to the clear terminal.

CONSTITUTION: An input signal S10 has the waveform shaped by a Schmitt trigger circuit 1 and is inputted to a shift register 20 as a signal S12. The register 20 has a functional constitution to obtain four-stage shift outputs of the input signal and outputs signals S13∼S16. Signals S13∼S16 are processed in a four-input AND gate 30 by AND operation and are processed in a four-input OR gate 40 by OR operation. Processing outputs S18 and S17 are given to terminals CK and CLR of a D-FF circuit 5 with clear respectively, and the output where noise is eliminated is obtained from the output of the circuit 5. Thus, the circuit having the noise eliminating characteristic is constituted of a digital integrated circuit and the circuit is easily made into a high density integrated circuit.