The present invention relates to a transparent polypropylene based sheet and its manufacturing method capable of: providing proper properties as a transparent sheet such as tensile characteristic, impact resistance, rigidity and little generation of whitening when being folded as well as maintaining transparency; preventing generation of a gum-like material in molding; and realizing continuous production. A manufacturing machine 1 includes: an extruding unit 11 for melting and kneading a raw material and extruding the material into a sheet-like shape; a first cooling unit 12 for cooling the melted sheet-like resin composition 20a to obtain a sheet (sheet-like article) 20; a preheating unit 13 for reheating the sheet 20; a heat treatment unit 14 for heat-treating the sheet-like resin composition 20; and a second cooling unit 15 for cooling the heat-treated sheet 20. The raw material of a resulting sheet 21 contains a polypropylene resin (a) and a metallocene-type ethylene-.alpha.-olefin copolymer (b).