A measurement part controls power supplied to a heater such that a temperature of the heater becomes constant by using a heater controller, and measures the supplied power in an unignited state in which plasma is not ignited and a transient state in which the power supplied to the heater decreases after plasma is ignited. A parameter calculator performs fitting on a calculation model, which includes a heat input amount from the plasma as a parameter, for calculating the power supplied in the transient state by using the power supplied in the unignited state and the transient state and measured by the measurement part, and calculates the heat input amount. An output part configured to output information based on the heat input amount calculated by the parameter calculator.