Engine exhaust emission control device and engine exhaust emission control method

[Problem to be Solved by the Invention] To suppress discharge of NOx into the atmosphere, when an abnormality occurs in an engine or an SCR device. [Means for Solving the Problem] An engine C/U 51 detects an abnormality which has occurred in an engine, and outputs a signal that indicates the occurrence of this abnormality to an SCR-C/U 61. The SCR-C/U 61 increases and decreases the urea water injection quantity corresponding to the abnormality which has occurred. On the other hand, the SCR-C/U 61 detects an abnormality that has occurred in the SCR device, and outputs a signal that indicates the occurrence of this abnormality to an engine C/U 51. The engine C/U 51 controls an engine part such as an EGR valve, to reduce the NOx emission amount.