An ignition device capable of more reliably protecting a primary winding of an ignition coil from high temperature is provided. The ignition device includes an ignition coil, a switching element, a temperature sensor, and a thermal cutout circuit. A primary winding of the ignition coil is connected to a DC power supply and the switching element. The temperature sensor is provided to measure the temperature of the switching element. The thermal cutout circuit forcibly turns off the switching element when the temperature of the switching element becomes higher than a predetermined forcible turn-off temperature Toff. The thermal cutout circuit is configured to lower the forcible turn-off temperature Toff when the power supply voltage Vb of the DC power supply decreases.