To provide an exhaust emission control device for a diesel engine capable of accurately determining timing for starting of reproduction of a particulate trap filter, regarding the exhaust emission control device for the diesel engine, more particularly, regarding a technique for determining optimum timing for the starting of the reproduction of the filter.

This device is provided with a storage means for storing a correspondence relation with particulate scavenging amount per unit time, a collation means for determining particulate scavenging amount per unit time in an operation region detected by a load detection means and a speed detection means by referring to the storage means, a cumulative means for determining particulate accumulation amount by accumulating the particulate accumulation amount, and a determine means for determining whether or not the particulate accumulation amount is more than a predetermined threshold value. A filter reproduction means raises the temperature of the filter when the particulate accumulation amount is determined to be more than the threshold value.