A forced regeneration device which performs regeneration of a particulate filter includes oxidation catalysts (23, 24a) disposed upstream from the particulate filter or in said particulate filter and a burner (30) located upstream from the oxidation catalysts and operable switching between a combustion mode for combusting a fuel spray by inflammation to raise temperature of exhaust gases in an exhaust passage and a fuel supply mode for supplying only a fuel spray to the exhaust passage without inflammation. After the burner operates in the combustion mode, the burner operation is switched to the fuel supply mode.