To continue a function for reducing NOx by properly applying a desulfurization to a three-way catalyst even when a high sulfur fuel is used in an exhaust emission control device in which the three-way catalyst having NOx and NH3 adsorbing property is applied to a diesel engine, NH3 is generated from NOx in the accelerator off state during the operation of an engine, and adsorbed and stored by the three-way catalyst, and the NOx in the exhaust gas is reduced and purified using the NH3.

An exhaust emission control device comprises a regenerating flow passage 20 having an oxidation catalyst 19 further on the upstream side than the three-way catalyst 14 and also having a fuel adding valve 15 (fuel adding means) further on the upstream side than the oxidation catalyst 19, and guiding the exhaust gas 9 to the three-way catalyst 14 via the oxidation catalyst 19; and a normal flow passage 21 directly guiding the exhaust gas 9 to the three-way catalyst 14 while bypassing the oxidation catalyst 19. Normally, the normal flow passage 21 is selected by a butterfly valve 22 (flow passage selector means), and the regenerating flow passage 20 is selected when a desorbing treatment is applied to the three-way catalyst 14.