The present invention provides a single-layer shape retaining material which is a fibrous, band-like, or sheet-like stretched formed material comprising 100 parts by weight of a high-density polyethylene resin having a weight-average molecular weight of 100,000 to 500,000 and a density of 0.945 to 0.960 g/cm3 and 3 to 50 parts by weight of an ethylene-α-olefin copolymer obtained by copolymerizing ethylene with an α-olefin having 4 to 10 carbon atoms, the copolymer having a density of 0.935 to 0.960 g/cm3, the difference in density between the copolymer and the high-density polyethylene resin being ±0.020 g/cm3 or less and a method for producing same.