A shaped article having a refractive index of not less than 1.625 at least in one direction and possessing excellent physical properties and various uses, which can be prepared by stretching a molded product, which is made of a polymeric material comprising at least 80 mol% of the repeating units of the formula: ##STR1## and having an intrinsic viscosity of not less than 0.25 dl/g when measured in a mixture of phenol and sym.-tetrachloroethane in a weight ratio of 6 : 4 at 30.degree. C. and has a refractive index of not more than 1.610 at least in one direction, at a temperature of 120.degree. to 230.degree. C. with a stretch ratio of 2 to 20 in the same direction as the refractive index is measured, or by melt extruding the polymeric material at a temperature higher than 230.degree. C. and not higher than 360.degree. C. while or immediately followed by stretching with a deformation speed of not less than 20 times the speed of the melt extrusion.