An acrylonitrile-containing fiber includes 100 parts by mass of a polymer including at least 15 parts by mass of acrylonitrile; and 1.0 to 50 parts by mass of a water absorbent resin having a pure water absorption capacity (gig) with respect to its own weight of at least 10 but less than 100, wherein the fiber is dyeable with a disperse dye.