A plasma generation device comprising: a plasma head configured to eject plasma gas that is plasmatized; a gas supply device (74;86) configured to supply gas serving as the plasma gas to the plasma head; a pair of electrodes (24,26), being provided in the plasma head, which is configured to perform discharging to a part of the gas supplied from the gas supply device (74;86) so as to generate the plasma gas; a temperature sensor, being provided in the plasma head, which is configured to measure a temperature of the plasma head; and a control device, wherein the control device executes a cooling process of cooling the plasma head by causing the gas supply device (74;86) to continue supply of the gas after the discharging of the pair of electrodes (24,26) is stopped, characterized by a heater that is provided in the plasma head, the heater being configured to heat a part of the gas supplied from the gas supply device (74;86) to generate high-temperature gas, wherein the plasma head ejects the high-temperature gas along with the plasma gas, wherein the temperature sensor measures a temperature of the high-temperature gas before the discharging is stopped, and measures a temperature of the heater as the temperature of the plasma head after the discharging is stopped, wherein the control device executes the cooling process until the temperature sensor measures a temperature equal to or less than a predetermined value after the discharging of the pair of electrodes (24,26) is stopped, and wherein the control device executes the cooling process after heating using the heater is stopped in addition to stoppage of the discharging. a plasma head configured to eject plasma gas that is plasmatized; a gas supply device (74;86) configured to supply gas serving as the plasma gas to the plasma head; a pair of electrodes (24,26), being provided in the plasma head, which is configured to perform discharging to a part of the gas supplied from the gas supply device (74;86) so as to generate the plasma gas; a temperature sensor, being provided in the plasma head, which is configured to measure a temperature of the plasma head; and a control device, wherein the control device executes a cooling process of cooling the plasma head by causing the gas supply device (74;86) to continue supply of the gas after the discharging of the pair of electrodes (24,26) is stopped, characterized by a heater that is provided in the plasma head, the heater being configured to heat a part of the gas supplied from the gas supply device (74;86) to generate high-temperature gas, wherein the plasma head ejects the high-temperature gas along with the plasma gas, wherein the temperature sensor measures a temperature of the high-temperature gas before the discharging is stopped, and measures a temperature of the heater as the temperature of the plasma head after the discharging is stopped, wherein the control device executes the cooling process until the temperature sensor measures a temperature equal to or less than a predetermined value after the discharging of the pair of electrodes (24,26) is stopped, and wherein the control device executes the cooling process after heating using the heater is stopped in addition to stoppage of the discharging.