A power steering apparatus comprises a main valve member rotating in response to the action of a fluid pressure motor supplementing manual steering torque and a flap valve member rotating in response to the manual steering torque and mounted within the main valve member. The main valve member and the flap valve member are operable to control flow of fluid under pressure supplied into and discharged from the fluid pressure motor. A plunger member is slidably received in the flap valve member and is provided with an anti-vibration member. A passage communicating with a fluid supply port is provided for applying fluid under pressure to the plunger member to urge the anti-vibration member against the main valve member.
