PURPOSE: To provide a control valve unit for use in power steering system, which is made of three plate valves, whereby it is enabled to make its machining easy and to manufacture the same economically.

CONSTITUTION: Control valve unit of this invention is made of three plate valves 17, 18, 19. Here, arrangement is such that middle plate valve 18 is rotated with the steering handle whereas valves 17, 19 on the opposite sides are rotated with output shaft 4. The valve 18 is formed with a first thru-hole 35 always supplied with hydraulic pressure and a second thru-hole 36 communicated to a drain passage. Valves, 17, 19 on the opposite sides, on the other hand, are respectively formed with annular grooves 23, 23' and 24, 24' at positions facing the thru-holes 35 and 36. At neutral position of the handle, plates 17, 19 are turned angularly to the middle plate 18 an equal angle in opposite directions to each other, and relative angular positions of these valves 17, 18, 19 are determined such that the first thru-hole 35 overlaps partially with the first annular grooves 23, 23', whereas the second thru-hole 36 overlaps partially with the second annular grooves 24, 24'. At the same time, grooves 23, 23' are connected to respective oil chambers 6, 7. Because of the arrangement that control valve unit of this invention is made of three plate valves, it is enabled to rendering machining easy and to manufacture the same economically.