A damper valve for a hydraulic power steering device is disposed on a hydraulic oil circuit for connecting an oil passage changing-over valve in a gear box and left and right oil chambers of a power cylinder, and is provided with a partition plate member for partitioning the interior of a valve casing into two valve chambers. The partition plate member is formed at equal intervals along a peripheral direction with a plurality of through holes. A first valve spring plate for opening/closing every other one of the plurality of through holes is fixed to one wall face of the partition plate member facing a first valve chamber of the two valve chambers positioned on the oil passage changing-over valve side, while a second valve spring plate for opening/closing the other every other one of the plurality of through holes is fixed to the other wall face of the partition plate member facing a second valve chamber of the two valve chambers positioned on the power cylinder side. The outer diameter of a first flat washer 38 for pressing the first valve spring plate is made larger than that of a second flat washer which holds the second spring plate, and the spring force of the first valve spring plate is made stronger than that of the second spring plate.