A hydraulic circuit structure of a work vehicle capable of solving a problem in a conventional structure wherein, in a machine attitude control in back hoe operation, pressure oil is preferentially fed to light-loaded machines and some work machines are slowly moved or stopped and, accordingly, the attitudes of the machines cannot be rapidly controlled and work performance is affected. To solve this problem, the hydraulic circuit of the work vehicle comprises two valve groups for a loader and a back hoe having circuits to supply the pressure oil from one hydraulic pump to a valve group for back hoe control through a valve group for loader control and the pressure oil from the other hydraulic pump directly to the valve group for back hoe control. The pressure oil is independently supplied from the hydraulic pumps to valve sections for controlling right and left stabilizer cylinders installed in the valve group for back hoe control.