Power steering device

Right-turn and left-turn aimed input shaft drive mechanisms are provided, each comprising a piston unit that slides in a bore formed in an output shaft and a contact surface that is formed on an input shaft. Under normal cruising of a vehicle, a comfortable steering feeling is given by a relatively small counter torque that is produced by a contact between the piston unit and a second inclined surface of the contact surface, and upon stray running of the vehicle due to doze in driving or the like, a relatively large steering torque is produced by a contact between the piston unit and a first inclined surface of the contact surface. An inclination angle of the second inclined surface relative to a traveling path of the piston unit is greater than that of the first inclined surface.