The present invention provides a Schmitt trigger circuit in which chattering does not occur in the output of the Schmitt trigger circuit even when it is connected to a communication bus without impedance matching and reflected noise is superimposed on the input signal. The Schmitt trigger circuit includes: a first signal detection circuit; a second signal detection circuit; a latch circuit; a selection signal generation circuit; a first input port; and a first output port. The first signal detection circuit is connected to the first input port, the latch circuit and the selection signal generation circuit. The second signal detection circuit is connected to the first input port, the latch circuit and the selection signal generation circuit. The latch circuit is connected to the selection signal generation circuit and the output port. The selection signal generation circuit includes a delay circuit.