CONSTRUCTION MACHINE

An exhaust pipe (7A) in an engine (7) is provided with an exhaust gas purifying device (10) with a urea selective reduction catalyst (13A) removing nitrogen oxides in an exhaust gas. The exhaust gas purifying device (10) is provided with a urea water injection valve (14) that injects urea water as a reducing agent to the upstream side of the urea selective reduction catalyst (13A). The urea water injection valve (14) is connected to a urea water tank (22) through a urea water pump (25). The urea water pump (25) is arranged in an upper side to the urea water tank (22). A return conduit line (30) in which the urea water flows from the urea water pump (25) toward the urea water tank (22) is disposed in an upper-lower direction between the urea water pump (25) and the urea water tank (22).