A rotary guiding device includes a rotating shaft to rotationally drive a tool head. The rotating shaft includes upper and lower shaft portions, and a steerable portion, the upper shaft portion and the lower shaft portion are steerably connected by the steerable portion. A non-rotating body is mounted on the upper shaft portion, the non-rotating body is substantially non-rotating with respect to the rotating shaft in circumferential direction when the rotating shaft rotationally drives the tool head. The lower shaft portion includes a rib portion coinciding at least partially in axial direction with the non-rotating body. The non-rotating body includes at least three hydraulic driving mechanisms uniformly distributed along its circumferential direction, the three hydraulic driving mechanisms controllably generate radial drive forces respectively, the radial driving forces act on the rib portion overlapping the non-rotating body so the lower shaft portion can be deflectable relative to the steerable portion.