An electrostatic discharge circuit includes a trigger section configured to detect voltage drops occurring by an electrostatic current transmitted to first and second voltage lines, and to provide pull-up and pull-down detection voltages, an auxiliary discharge section configured to operate by the pull-up and pull-down detection voltages, and to discharge the electrostatic current introduced through an input/output pad to the first and second voltage lines, a main discharge section configured to operate by the pull-down detection voltage, to electrically connecting the first and second voltage lines, and to discharge the electrostatic current, and a CDM discharge section configured to operate by the pull-down detection voltage, and to discharge the electrostatic current supplied from the input/output pad to an internal circuit.