There are provided a Schmitt trigger circuit that has hysteresis characteristics in which a release point and an operating point are determined based on a width of an inputted pulse. The Schmitt trigger circuit may include a signal/pulse conversion unit that receives an analog signal to generate an input pulse having a width corresponding to a magnitude of the analog signal, a pulse width determination unit that compares the width of the input pulse generated in the signal/pulse conversion unit with a predetermined first threshold width and a second threshold width greater than the first threshold width to output state information indicating the compared result, and an output determination unit that outputs a high signal, when the width of the input pulse is changed from a state of being smaller than the second threshold width to a state of being greater than the second threshold width based on the state information, and outputs a low signal when the width of the input pulse is changed from a state of being greater than the first threshold width to a state of being smaller than the first threshold width based on the state information.