A washer tank is integrally formed with a front air duct, and the washer tank and the front air duct are installed within a cab. Thus, the washer tank can be installed within the cab by the use of spaces around the air duct. This arrangement makes it possible to install the washer tank within the cab in an unintrusive way and in the vicinity of a washer liquid spout nozzle without necessitating to provide an installation space exclusively for the washer tank.