In a hydraulic excavator, in a rear part of an upper rotating body (2) mounted on a lower traveling body is disposed an engine room (12), and in a front surface of a partition wall for partitioning the front surface side of the engine room from the exterior is provided a step (21) serving as a foothold for opening and closing a bonnet (18) and performing maintenance work. On the lower side of the step (21), a duct (D) for exhausting the air within the engine room (12) to the exterior is formed in a state that the step serves as an upper surface wall of the duct.