The urea water pipe clogging detection device for urea SCR can accurately detect whether or not clogging has occurred in a urea water pipe extending to a dosing valve adapted to spray urea water. In order to detect the clogging in the pipe segment extending from a supply pump (18) to the dosing valve (12), the clogging detection device includes a urea water sensor (22) which detects urea water temperature in a urea water tank (15), a pressure sensor (27) which detects pressure in a pressurized urea water feed line (20), an exhaust gas temperature sensor (26) disposed in an exhaust pipe (10) upstream of an SCR device (11), and clogging determination means (33). When a key switch is turned on, the clogging determination means performs a startup control to drive the supply pump (18) and increase the pressure in the pipe segment. Subsequently, if a detection value of the exhaust gas temperature sensor (26) is less than or equal to a predetermined temperature, and a detection value of the urea water sensor is greater than or equal to a freezing temperature, then the clogging determination means performs emptying control for returning the urea water from the pipe segment to the urea water tank (15), and detects the clogging of the pipe segment from the detection value of the pressure sensor during the emptying control.