PURPOSE: To make it possible to obtain a printing body imparting sharp printing and excellent in heat ageing resistance, by setting the depth from the surface to be printed of a polyacetal resin molded body to the internal perfect spherulitic layer thereof to 200μm or less.

CONSTITUTION: The cross-sectional structure of the polyacetal resin molded body, which is obtained by performing the injection molding of a polyacetal resin in a mold of which the surface temp. is set, for example, to 110W115°C, perf., 120W140°C, has a surface to be printed wherein a crystal is grown from the surface thereof toward the interior thereof and the depth from the surface of the uppermost layer thereof to the perfect spherulitic layer (e) is 200μm or less. Penetration printing is performed by utilizing a method wherein printing is directly applied to the surface to be printed of the molded body by dry offset printing, screen printing or pad printing before heat treatment or by a method wherein the ink on release paper is placed on the surface to be printed of the molded body prior to performing thermal bonding under pressure. In the injection molding of the polyacetal resin, the surface temp. of the mold is raised in order to smooth surface appearance, to enhance gloss and to enhane the sharpness or heat ageing resistance of printing in a penetration printing body.