A urea water supply device supplying urea water to purify exhaust gas from an electric power generating engine. The urea water supply device includes: a urea water injector; a urea water flow route in which urea water flows; a clean water supply route in which clean water flows; and a urea water amount adjustment valve and a urea water flow meter provided in the urea water flow route. The clean water supply route merges with the urea water flow route on the downstream side of the urea water amount adjustment valve and the urea water flow meter.