A diagnostic system designed such that an aggregate of parameter combinations is stored, which is an aggregate of combinations of parameters consisting of a first parameter for determining the output of the high-frequency power source, a second parameter for determining the flow rate of the carrier gas in the aerosol, and a third parameter for determining the distance between the plasma torch and the interface, and which forms a specific array such that the measurement points corresponding to the respective combinations are lined up in order along the direction of length of an envelope that forms the end on the high-sensitivity side of a graph drawn as an aggregate of all measurement points on a sensitivity-oxide ion ratio graph, and a diagnostic measurement is performed with a specific diagnostic sample using the parameter value of each combination of the above-mentioned parameter combinations that form the aggregate such that the device properties can be confirmed from the position on the envelope on the sensitivity-oxide ion ratio graph of the actual measurement points corresponding to each combination.