PROBLEM TO BE SOLVED: To suppress a supply malfunction of urea water as much as possible, in the filling control of the urea water in a urea water supply system of a pump sharing type having two supply valves.SOLUTION: In a urea water supply system of a pump sharing type having first and second supply valves, a urea water tank and the supply valves are connected to each other by a urea water supply route which includes a first supply route for the first supply valve, and a second supply route which is a supply route for the second supply valve, and larger than the first supply route in a route capacity by a prescribed capacity. Then, at the filling control of urea water, the urea water is pressure-sent to the first supply valve and the first supply route by a pump which is in a prescribed drive state in a state that at least the first supply valve out of the first supply valve and the second supply valve is opened, and the first supply valve is closed on the basis of a pressure value which is acquired by acqu
