Disclosed is an optical-fiber preform having barrier layers to hydroxyl radicals, the optical-fiber preform comprising: a quartz tube in the form of a cylinder shape serving as a substrate for forming the optical-fiber preform; a first barrier layer for preventing hydroxyl radicals from permeating the optical-fiber preform and deposited onto the inner surface of the quartz tube; a second barrier layer having a permeation coefficient higher than the first barrier layer and deposited onto the first barrier layer; a third barrier layer having a permeation coefficient lower than the second barrier layer and deposited onto the second barrier layer; and, a core layer being located at the center of the optical-fiber preform.