A wall flow type particulate filter is arranged inside the exhaust passage of an internal combustion engine where combustion is performed under an excess of oxygen. The particulate filter carries a solid acid. The solid acid has a Hammett acidity function smaller than −0.83 and larger than −12 in the standard state. To remove the ash from the particulate filter, ash atomization processing for rendering the state of the particulate filter a state where the exhaust gas which flows into the particulate filter is lowered in concentration of oxygen and the particulate filter is raised in temperature is temporarily performed.