an exhaust gas measuring apparatus includes an atmosphere introducing unit , an air purifier , a diluting unit , selecting means , a sampling unit , and measuring means . the atmosphere introducing unit takes in air in the atmosphere as diluting air . the air purifier takes in and purifies air in the atmosphere , thereby generating diluting air . the diluting unit dilutes a portion of exhaust gases of an engine with the diluting air . the selecting means causes either one of the atmosphere introducing unit and the air purifier to communicate with the diluting unit . the sampling unit collects diluted exhaust gases . the measuring means obtains the emission amount of collected exhaust gases .