To prevent damage and early wear of oxidation reaction granules, catching and burning particulate discharged form an engine, caused by collision and rubbing when the oxidation reaction granules is relatively moved by thermal expansion in a storage chamber.

This particulate filter has an oxidation reaction chamber 3 into which exhaust gas flowing in from an inlet 2 is led, and an ash accumulating chamber 4 downstream from the oxidation reaction chamber 3. In the oxidation reaction chamber 3, the oxidation reaction granules 23 to which particulates adhere so as to catch and oxidize the particulates are stored between an outer peripheral cylinder portion 17 and an inner peripheral cylinder portion 18, and can be heated up by a heater 27. The oxidation reaction granules 23 is pressurized by pistons 20, 22 energized with a spring 21 from an end portion. Therefore, if intervals between granules tries to expand too much due to thermal expansion and the like, the pistons 20, 22 narrow the intervals, thereby preventing collision and rubbing of the each granule 23.