An atmospheric pressure plasma device including a plasma head; a gas tube configured to supply a gas to the plasma head; a flow rate controller configured to control a flow rate of the gas supplied to the gas tube; a pressure sensor arranged downstream of the flow rate controller and configured to detect a pressure in the gas tube; and a determining section configured to determine a state of the device based on how the pressure in the gas tube deviates from a standard value specified for each flow rate of the supplied gas. As a result, it is possible to determine the gas leakage of the atmospheric pressure plasma device. Further, it is possible to determine whether plasma is being generated in a favorable state.