PURPOSE: To perform highly accurate measurement with a miniaturized equipment, by constitution the titled apparatus in such a manner that an exhaust gas in an exhaust gas introducing pipe is maintained at a dew-point temperature or higher and also, the liquid minute particle other than moisture in the exhaust gas is arrived at a filter without vaporization.

CONSTITUTION: A suction pipe 8 is connected to an exhaust gas introducing pipe 2 inserted into an exhaust pipe 1 of a diesel engine. The flow rate of exhaust gas flowing back a by-pass pipe 16 is controlled by a controller 19 basing on the detected value of a differential pressure gauge 20 and the flow rate of the exhaust gas feeding to a gas meter 15 is kept constant. A filter 21 is provided on the surface of a filter holder 9 and the minute particles in the exhaust gas are collected. The temperature of the exhaust gas is kept at a prescribed value by controlling a heater 22 and a heat exchanger 23 by a controller 26 basing on a detected temperature of a temperature sensor 29 and controlling a heater 24 by a controller 27 basing on the detected temperature of a temperature sensor 30.