To provide a simple manufacturing method of a ribbed heat-resistant resin sheet.

This manufacturing method has a molding process wherein a liquid resin material 46 is supplied to the inner surface of a mold 40 having grooves 44, which are formed by either one of parallel ribs (a) with a width of 200 μm or below and a depth of 500 μm or below formed at an equal interval pitch of 1 mm or below, lattice-like ribs (b) with a width of 200 μm or below and a depth of 500 μm or below formed at longitudinal and lateral pitch intervals of 1 mm or below and meandering ribs (c) with a width of 200 μm or below and a depth of 500 μm or below formed at a pitch interval of the opposite side of 1 mm or below, and heated and solidified to mold the ribbed heat-resistant resin sheet having continuous ribs or lattice-like ribs on its one side. A mold is formed of a glass material and, as a molding method, a centrifugal molding method is preferable and the mold 40 is constituted of a reinforced outer cylinder part 41 and a molding part 45 made of glass.