Provided is a urea water consumption diagnostic device for urea SCR, which is capable of detecting normal and abnormal spraying of urea water from a dosing valve. The urea water consumption diagnostic device for urea SCR draws urea water from a urea water tank (15) using a supply pump (18), and sprays the same from a dosing valve (12) provided upstream of an SCR device (11) via a pressurized urea water feed line (20). The urea water consumption diagnostic device includes a NOx sensor (13) disposed downstream of the SCR device (11), NOx purification rate determination means (34) configured to receive a detection value from the NOx sensor (13) and determine from the detection value whether the NOx purification rate is within a prescribed value range, and abnormality diagnostic means (33) configured to determine a difference between the urea water spray volume amount sprayed from the dosing valve (12) and a urea water consumption volume in the urea water tank, and also determine whether there is clogging of urea
