PURPOSE: To miniaturize a valve device by utilizing a confluence valve for switching- right and left control valves for running to low-speed, or high-speed conditions, and by supplying confluence oil pressure constantly to a control valve for service port.

CONSTITUTION: A center-bypass type multiple left valve VL is provided, while a control valve 1 for service port is located on the lower side of an oil passage of a control valve 5 for left running, which is connected to a first hydraulic pump P1. A multiple right valve VR having a control valve 9 for right running, is provided and is connected to a second hydraulic pump P2. A two-point switching confluence valve 11 having three-connection oil passage is arranged between a first oil passage 17 of the valve VL and a second oil passage 18 of the valve VR. At a low-speed point of the valve 11, oil is individually transported from the pumps P1, P2 to the valves 5, 9, so as to maintain low-speed condition, while confluence pressure oil is supplied to the valve 1 through a confluence passage 12 and a connection passage 15. While a pressure oil confluenced at the valve 11 is transported in the order of the valves 9 and 5 at a high-speed point, an exhausting port 16 is closed so as to maintain a high speed condition, and the oil is supplied to the valve 1 again. A large laying working machine is thus installed on a small type machine.