In a hydraulic excavator wherein a control valve unit having a plurality of control valves in a united form and an operation pattern switching valve for switching from one to another among combined patterns of operating valves and control valves are disposed side by side in front and rear positions respectively within a valve accommodating space formed between an upper frame base plate and a floor plate in an upper rotating body, the operation pattern switching valve is inclined forwardly downward in a state in which its upper surface side including an operating lever thereof faces an operation port being formed to the floor plate.