<p>A filter (7) for collecting particulates in exhaust is provided to an exhaust passage (14) of an engine (10). A temperature sensor (8) for detecting the exhaust temperature is provided in proximity to the downstream end face of the filter (7). Also provided is a concentration sensor (9) for detecting the oxygen concentration of a gas mixture in which exhaust passing through a center part (71) and a peripheral part (72) of the filter (7) is mixed. Further provided is a determination means (3) for determining the position of active particulate combustion in the filter (7) on the basis of the exhaust temperature detected by the temperature sensor (8) and the oxygen concentration detected by the concentration sensor (9).</p>
