To obtain large steering auxiliary force without increasing power loss and energy loss in a state where excessive load is not locally applied.
The power steering device is equipped with a steering shaft 2, an electric motor 4 as a first steering auxiliary means connected to the steering shaft through a speed reduction mechanism 22, a ball screw mechanism 5 converting the rotation of the steering shaft to the axial movement, and a sector gear 6 interlocking with the ball screw mechanism. The power steering device is provided with a second steering auxiliary means steer-assisting the sector gear 6 in addition to the electric motor 4. The second steering auxiliary means comprises a cylinder part 71 housing a ball screw mechanism 5 and a hydraulic supply circuit 9 which supplies pressure oil into the cylinder part 71 and axially moves the ball screw mechanism 5.
NISHIZAKI KATSUTOSHI
HAMANO KENICHI
