Abstract: The invention relates to a process for producing a thermoformable acrylic resin sheet having a granite-like appearance after thermoforming, wherein ground particles of a methyl methacrylate resin which has been slightly cross-linked by means of 0.005-0.2 wt. % of a polyfunctional monomer, said particles having a size smaller than 1 mm, are incorporated in an amount of 0.3-1.5 wt. % into a liquid methyl methacrylate matrix resin composition containing a cross-linking monomer in an amount which is sufficient for effecting cross-linking of the matrix resin to a degree which is equal to or higher than the degree of cross-linking of the ground resin particles, at least one of the resin particles and the matrix resin composition containing a coloring material providing a color difference between them, whereupon the liquid mixture is brought into a flat mold and is kept therein to allow the resin particles to settle and the mixture is then polymerized to produce the thermoformable acrylic resin sheet.