A hydraulic power steering apparatus is provided with a check valve regulating a back flow of a working fluid from a power cylinder mechanism to a hydraulic pump side. A valve element slidably accommodated within a valve body of the check valve has three guide portions protruding to an outer side in a diametrical direction. A valve internal oil path in which the working fluid circulates by a pair of guide portions adjacent in a peripheral direction is formed in the valve element. The guide portion is constituted by a slidable contact portion having a sidable contact surface surface contacted with an inner peripheral surface of the valve body, and a coupling portion coupling a base body portion and the sidable contact portion. A width (W1) in a peripheral direction of the sidable contact surface is larger than a width in the peripheral direction of the coupling portion.