Exhaust emission control device

A control unit activates regeneration assist means, if a specific operating state involving incomplete combustion of particulates by NO 2 continues for a predetermined period or more, as a first determination condition, and controls an exhaust gas temperature or a temperature of a catalyst to enhance the conversion efficiency of the catalyst into NO 2 , thereby continuously regenerating the particulates. The control unit activates forced regeneration means, if a deposited amount of particulates detected by deposited amount detecting means exceeds a predetermined value, as a second determination condition, and controls the exhaust gas temperature or a temperature of a filter to be higher than that of when the regeneration assist means is activated to forcibly regenerate the filter. The control unit activates either the forced regeneration means or the regeneration assist means in accordance with the temperature sensed by temperature sensing means, if the first and second determination conditions are simultaneously established.