The present invention is adapted to be provided with: a first sampling line for sampling raw exhaust gas; a first concentration measuring part that measures the concentration of the predetermined target component contained in the raw exhaust gas; a second sampling line for sampling diluted exhaust gas; a second concentration measuring part that measures the concentration of the target component contained in the diluted exhaust gas; and an arithmetic unit that, with use of first measured concentration, second measured concentration, and a diluted exhaust gas flow rate, calculates a raw exhaust gas flow rate, wherein in a state where the first sampling line and the first concentration measuring part are heated, the first concentration measuring part measures the concentration of the target component contained in the raw exhaust gas.