An atmospheric plasma generator, configured to generate plasma by a discharge between a pair of electrodes (24, 26), comprising: a main housing comprising a reaction chamber, wherein the electrodes (24, 26) are disposed so as to face each other inside said reaction chamber of the main housing; a process gas supply device for supplying a process gas to the reaction chamber, said process gas supply connected to the reaction chamber; a heated gas emission device comprising a heated gas supply device for supplying a gas to be heated to a heated gas supply path, and a heater disposed in the gas supply path to heat the gas to be heated; a current sensor configured to detect the quantity of power supplied to the electrodes (24, 26); flow rate controllers (103, 104) configured to measure the flow rate of a reaction gas supplied to the reaction chamber and the flow rate of the heated gas, respectively; a first pressure sensor configured to detect the pressure of the process gas supplied to the reaction chamber from the process gas emission device, a second pressure sensor configured to detect the pressure of the heated gas supplied from the heated gas supply device; a temperature sensor attached the heater and configured to measure the temperature of the heated gas, said current sensor, flow rates controllers (103, 104), first and second pressure sensors and temperature sensor configured as detectors configured to detect an abnormality based on at least one of the detected values; a storage device; and a control device, wherein the control device stores the state of the plasma generator in the storage device in association with time, and executes a storage process for storing the state of the plasma generator in the storage device from a predetermined time before the detector detects the abnormality, to the time the detector detects the abnormality, wherein the control device executes an abnormal stoppage of the atmospheric plasma generator by stopping supplying power to the electrodes (24, 26) and stopping supplying the process gas and the heated gas, when the detector detects an abnormality and stores the state of the atmospheric plasma generator from the time at which the abnormality is detected, to the time at which the abnormal stoppage is executed. a main housing comprising a reaction chamber, wherein the electrodes (24, 26) are disposed so as to face each other inside said reaction chamber of the main housing; a process gas supply device for supplying a process gas to the reaction chamber, said process gas supply connected to the reaction chamber; a heated gas emission device comprising a heated gas supply device for supplying a gas to be heated to a heated gas supply path, and a heater disposed in the gas supply path to heat the gas to be heated; a current sensor configured to detect the quantity of power supplied to the electrodes (24, 26); flow rate controllers (103, 104) configured to measure the flow rate of a reaction gas supplied to the reaction chamber and the flow rate of the heated gas, respectively; a first pressure sensor configured to detect the pressure of the process gas supplied to the reaction chamber from the process gas emission device, a second pressure sensor configured to detect the pressure of the heated gas supplied from the heated gas supply device; a temperature sensor attached the heater and configured to measure the temperature of the heated gas, said current sensor, flow rates controllers (103, 104), first and second pressure sensors and temperature sensor configured as detectors configured to detect an abnormality based on at least one of the detected values; a storage device; and a control device, wherein the control device stores the state of the plasma generator in the storage device in association with time, and executes a storage process for storing the state of the plasma generator in the storage device from a predetermined time before the detector detects the abnormality, to the time the detector detects the abnormality, wherein the control device executes an abnormal stoppage of the atmospheric plasma generator by stopping supplying power to the electrodes (24, 26) and stopping supplying the process gas and the heated gas, when the detector detects an abnormality and stores the state of the atmospheric plasma generator from the time at which the abnormality is detected, to the time at which the abnormal stoppage is executed.