Provided is a urea water consumption diagnostic device for urea SCR, capable of detecting if a pressurized fluid feed line or a dosing valve has been clogged or stuck with a foreign matter, or if the urea water has been left to continue spraying from the dosing valve. The urea water consumption diagnostic device for urea SCR includes a urea water sensor (22) that detects a level of the urea water (U) in a urea water tank (15), spray volume instruction means (30) that instructs a volume of urea water to be sprayed from the dosing valve (12) in accordance with NOx in an exhaust gas, instructed spray volume addition means (31) that adds up the instructed spray volumes instructed by the spray volume instruction means (30), consumption volume calculation means (32) that calculates a cumulative consumption volume (D) from a detection value input from the urea water sensor (22), and abnormality diagnostic means (33) that compares a cumulative instructed spray volume (P) from the instructed spray volume addition mean
