A hydraulic power steering apparatus 1 which is arranged so that a damper valve 10 is disposed in hydraulic oil circuits 8 and 9 for connecting an oil passage selector valve 11 in a gear box with right and left oil chambers of a power cylinder 6. The damper valve 10 comprises a spool valve. And a control oil chamber 21 of the spool valve 10 is connected with a hydraulic oil feed passage 18 for connecting a hydraulic pump 13 which is driven by an internal combustion engine so as to discharge hydraulic oil, with the oil passage selector valve 11. Its back pressure chamber 17 is connected with a hydraulic oil circulating passage 19 for connecting the oil passage selector valve 11 with a reservoir tank 12. Orifices 27 and 28 are provided in connecting oil passages 22 and 20, such that when discharge oil pressure of the hydraulic pump 13 rises, opening of the spool valve 10 increase.